T H E G E N E T I C S OF ~ I . R M A D I L L I D I U 3 I V ULGA.RE LATP~.

II. sTUDIES ON THE INKEP~ITANCE OF MONOGENY AND AMPHOGEN¥

Br H. W. IIOWARD

Schod of Ag~'ic~dtu~% Ca~nbridge

CONTENTS PAGI~

I. Introflu erich 143

I I . GenerM considerat io~ of mondgeny 114: (1) Vandel 's theory to account for monotonic broods 144 (:2) GenegieM segregations hi manogeni~ and ~mphogenie broods 144 (3) Variations ' in the sex re.tics of different broods from the same females i4~5

i t i . The inheritance of mono t ony and amphogeny 147 (1) Descendants of thelygemie female A . 148 (2) Descendants of thelygerac females CB and CO 148

(3) Descend£nts of thelygenie female DA 150 (4} I)eseendants of arrhenogenie female AB 150 (5) ]Descendants of amphogenie female EA t51. (6) Descendants of amphogenic female FB 152 (7) Summary and discussion . 152

IV. The effect, of monogeny on the composition of natura l populat ions 153 (1) ~[onogeny as a.n ontbreeding mechanism . . , 153 (2) The effeel~ of monogeny on sex ratios in natura l populat ions 154 (3) Possible s~abte t}~oes of populations ." 155 (4) ArTnagillidium populations 156

V. S u m m a r y 158

Befcrenees . .159

X. [NTIIODUCTI ON

Va.~ldeI (1.939) and Howard (t9~0) have reported the occu.rrenee of three types of'fema.lc i.n the woodlouse d~'mag.i~Zid{u~n ~ndgare--amphogerdc

(~/ :females wldoh produce broods consist, i~g of about 50 %; males plus o0/o females, thelygeuic females which produce broods oon.sisting a.lmost entirely of females, and arrhenogenic females w]fich produce broods co:u.sisbing aline,% entirely of males. Bo~h thelygenics and arrhenogenics are deseri.bed as monoge~ics.

¥andel (19:-38) has also described in some de~ail the inheritance of monotony in. the woodlouse fg,r/choniscus 2row:~oriu~. I-Ie cow, eluded ~hat the ~onogenic condition was inherited eytoplasmica[ly, t].u.'o u~h.~ the e~gsee, --Gnus monogeic :females prod~ee ni]]]~ mol.mgenic daught, ers and anaphogeie females only amphogenio daughters. Vandel a/so found tlha,% while :many of the 5la, t~ghters of a Uhelyge~ic female were thelygenios, others were arrl~.enogenics. Preliminary resul~,s for d.'r~nadil~id.i't.~'m wdga~'e (]-Ioward, 19,i0) suggesOed Chat :hi this woodlouse the inherJUa,noe of amphogeny and mono~eny was no[ cytoplasmic. The further results given hi ~he prose1% paper d,_~ indicate that~ monogeny and amphogeny

144 T h e 9e~,,,e~ic~' of A r m ~ d i l l i d i u m v u l g a t e Lcrh.

may be inherited 035eo]?]asmieally in A.r~~adil, l~idi,~mr. Ig appears, how- ever, to be a rather irreg~'tlar type of cytoplasmic inheritance in many oases, and it must also be pointed out that it i s v e r y diNeult to dis- t, ingnish in'woodliee, where the re:male is probably the heterozygous sex, between cytoplasmic inhsritan.ee and inheritance by factors in the I<ehroraosome, sines every daugilter receives her 2F-ehrom.osome as well as tier ey~oplamr~ :from her mother.

II. -GE~m~zL co~sm)J~m~Tioxs o~ ~O~O¢'E-VY

(i) FcL~wleFs &eory ~o c~cco~.~g lot m.o'~mge.~de broo&'

Va, adel (1938) fuund theft in the woodlom~e TrieAo~dsc't~s monogenie broods were as large as amphogeu~c broods. The absence of one sex in monogenic broods is therefore no~ due ~o animals of this sex dying before they are scored, or a~ some stags before birth. Vandel ~lso states bhat he ha,s never oBserved any cases of se.~ z'eversaI no," any intersexes in woodlioe. I t therefore seems nnlike]y that one-haft" of tt,e males in a~'rhenogenio broods and one-half of the .females in thelygsnio broods have the sex-chromosome constitutions of. the opposite sex. I t has also been shown (see Table X in I-reward, 19..1-0, and male AL in Table 6 of t~ s paper) that the male I?aren~ has no effect on the sex ratio of a brood;.for the same male can be {he paren~ of an a~'rhenogenic brood from one :femals and of a thetygenie. 1)rood from another, or of an ampho- genie brood from one female and of a thelygenis brood from another.

Vandel's theory (see Vgndel, I'958, 19gl) to account for monogenic ])~oods is simple. ~e suggests that in woodlics.the female is the hetero- zygous sex (chromosomes X Y ) , and that in monogenie females the cyto- plasm clireo~s the segregation of the sex chromosomes. Thus in thelygenio females every egg receiqes a Y-ehz'omosoms and the X-chromosome always goes into the first polar body, while in arrhenogenie femMss every egg receives an X-chromosome and the IF-chromosome Mwa.ys goes into the first polar Body.

It has, however, been pointed oat (t-Ioward; 1940) that th.s actual raeehanism by which .eve W animal in a 5helygenie bropd has a sex chromosome constitut!on of X Y and every animal in an arrhenogemc brood a constitution of X X may be different from that suggested By Va~del, and it has also been suggested in the introduction to this paper that the factors responsible for monogeny may be carried in ~he Y- chromosome and not in the cytoplasm,

(2,) 6%~ze~.icc~l a%q,reya,~io~z~ i't~ '~zo'e~.oye~ cmd ~m~/)hoye,n,.fc b'roo&,

Gene%ical results show that the segregation of the autosomes takes pJ.aee normally in {he eggs of both am.pl?ogenic a~.d. monogenie females (see Table 1), and a].so that the eggs of both amphoge~ic and monogenie femMcs are fertilized and do not dsvdop paa:thenogenetically (see T~ble 2), The exam.pies given in the two tables are for the domJnan~

H . W . HOWAgD 145

factor-red. Similar resuRs have been obtained for the two dominant factors for the sex-limRed types CY and D. The two resuRs in 2?able 2 ,which suggest that some eggs might develop parthenogenetically are alines{ cergainIy ~o be explained, by the fact tha~ sperms can be stored

females for at least a year. Evidence for such storage of sperms is also. given i~ Table 1 of Xoward (19~0)..~

Table 1. No,rma~ segregations jbr regv. b~aek i.n the eggs of ferneries heterozggous for the dmrdnant factor for red-

• Cons t i t ug ion o f b r o o d F e m M e N a l o ~-- .~ p a r e n t parent No. of ~iales P e m s l e s (red) (black) b r o o d ~ e d ; B l a c k l~ed : B l a c k

B 0 G 27 17 : 19 7 : l 0 B D O 28 8 : 8 15 : 19 13N SA 34 20 : 18 6 : 8 B O SA 39 10 ; 12, 8 : 6 JD ~. 45 20 ; 20 32 : 22 J ib S G ,I6 57 : ,.',i8 69 : 79 X O H]~ 64 8 : 3 I 1 : 4. J D (No ma le since brood 45) 65 9 : 10 8 : 10 X b i K L 71. 0 : 0 5 : 1 0 I C E I, DP 77 7 : 4 0 : 0 B D (No ~a. le s ince b r o o d 28) 90 15 : 7 t 5 ; I8 B F C A 94 1 1 : t 2 2 : 1 B Q A L 99 O: 6 I 0 : 1 5 B Y A L 109 5 : 8 8 : 7

B i ~ (No ma le s ince b r o o d 34) 127 9 : 13 9 : 12 J 'B B A 128 14: 6 1 7 : 8 IG/ XF 133 7: 7 O: 0

Table 2. Segrsgetio,ns for red v. bgaelc i~ broods from black females x he~erozggous ~sd males

C o n s t i t u t i o n of b rood F e m a l e 3¢Me ~ ......... - - - " , p~ren~ p a r e n t No, of N a l e s :Females (b lack) (red) b r o o d R e d : ~Bla,ck g o d : :Black

A B B 8 9 : 1 3 6 : 3 G A J A 37 0 : 0 6 : 7 C12, (]?,,ed male of same b rood ) "!.3 8 : 1 25 : 14 C D * 'C, C4 8.2 5 : 21 0 : 0 D]3 Ct:I: 95 19 : 32 0 : 0 :FEI'[" 0C_4 114 2 : I I 4 : g8 El" J D A :{.jS o : 0 .3 : 3 IOL J D C L D 8 : 7 4:', 1 (¢0 JD]3 154 2 : 0 9 : 6 E G .T]):B 155 l : ~ 23 : 24 G F ,T:DD t~J0 0 : 0 4. : 3 :D'@" l" {No ma.le since br m d 114) 163 0 : 9 1 : 1I ~Jal a D D Jglj l0 : 12 lJ: : 8

* .Brood 8.2--l lhere is a, s ignificant , defieJ.oJ~ey o f r eds J±t th i s b rood . F e m a l e CD w a s m a t e d wibb ~, bln,ek ma le t.h~, p r e v i o u s yee,r. S p e r m s h a v e p r o b a b l y s u r v h , ed t~:om t h i s p r e v i o u s m a t h l g (of, Tab le I of J ' lowm'd (1940)).

~" ldroods 114 a n d 16~. Fematc. F G w~s col lected d u r i n g the b reed ing sea.son and m a y h a v e b e e n a l r e a d y i m p r e g n a t e d b y a b l a c k ma le beJbre beh lg p l aced ~ ibh ma le CO.

(3} Vc:.rgation,~ ,g'n g/~.c sex ,ratios of d~i[/brc~ b'roods ,/?'om, the sa,~,~e /e,m,a.Zes

Yaude] (1939) fonnd ~hat the sex to,tics in t£te three broods per yeas" produced by Arma, dil.ggd,i~cm an, des French coz~d.J.tions varied greatly from brood fo brood (some of Vandel's resuRs are given in Table ~IlJ_ of Howard, 19~:0). Thus fema,le A 2 produced a first brood eonta,i~.iJ~g

J'o~{rn. o f CRenebics 44 l 0

146 q'he ge'net.ic~ • o f A r m a d i l l i d i u m v u t g a r e Lc~tr.

2-'1:'5% of males, ~ second containing 7~/u of males and a, third con- ~;aining 92 ~o of males.

Unde~ 0ambridge. IM)oratory conditions a few females produce two broods per year. tn Table 3 resaRs are given for seven pairs of broods

TM)le 3. £'e:c, ratio~ i'n jirat and second broods of I.ke sc~,~.~e y e a r Composif, i.on o f OomposibiOl~_ o f

N ~ m e o f No. o f firs~ b r o o d i%. of s econd b r o o d female firs'~ , second. : -<~ . ..-, p a r e n t b r o o d d,g :!~9 % '$'9 b r o o d ..~a :o ,2 3/0 ~ ? AJ 20 6 : 5 0 ~U 44 2 : 7 78 B G 3 t e.: 4 67 32 5 : 7 58 C~3B 116 L2 : 26 6S 130 4 : 9.5 86 COD 102 1 : 8 5 99 132 0 : -t 100 CO]:][ 117 i 4 : 17 55 129 94 : 27 53 F:B 5 i 94 : 10I 52 61 34 : 32 48 iklC* 11I i 8 : 2-1: 33 78 80 : 9 ].3

* HC was ~L F r e n c h ±'ema, te.

produced by ~h~ same re.toMes in one year. Unfortu~m, tely, s~veral of tam broods ~re very small ones. The results for females @BB~ C@l:l aJ~,fi. FB d% however, sugges{ that {h~re are no big changes [n sex ratios of successive broods l¥om the sam.~ female. I t is also interesting ~o note ~hat the g~enoh female }tO (give.n ~o me' by Prof. Valzdd) does show a change in the same direction as that found l~y Va, nd.el.

. In Table -I are given data for the sex ratios of broods frdm the same ~emMes in two snoeessive years. Of the twenty-two femMes, about fifteen

Table ¢. Se:v ratios in broods f rom same ]'ema!es in d,iffe~'e~t years B r o o d in firs~ y e a r B r o o d in. s e c o n d y e a r

f \ f - - - - ' x

Name of Composition (Jomposigion fema1~ ~ "~ r - - ~' - -

p a r e n t N o . c ~ : .co % o i ~ o . . $ ~ : o~ % o ?

A B 8 2 0 : 9 31 25* 4 0 : 1 2 A P 10 , 4 : 3 43 49 43 : I5 26 A J 2 6 + 4 4 8 : 5 7 88 69 9 : 0 0 [8D :~8 16 : 34 68 90 22 : 33 60 BG 31 +32 9: 9 50 122 7:11 61 BI~ 33 4 5 : 0 0 118 5 : 0 0 BN 34 38 : 14: 27 127 22 : 21 49 CBJ 88 2 : 32 94 167 1 : 7 88 CD 35 64=: 0 ,0 82 2 6 : 0 0 D B 23 1 7 : 5 0 75 95? 5 I : 0 0 D E 54 1.7 : 35 87 6 8 . 23 : 27 54 EA~ 83 7 : 2 22 158 7 : 0 0 F~2 22 0 : 49 i00 68 0 : 38 I00 FB 51 + 61 128 : 133 51 63 8 : 12 60 F0 56 9 : 129 94 72 0 : 45 I00 F D 53 9 : 7 44 112 0 : 53 I00 JYF 59 8 : 72 90 67 0 : 25 100 F~ 114 13 : 3~ 71 163 9 : 12 57 ,IB 46 105 : 148 58 128 20 : 25 56 3"D 45 40 : 54 57 ~5 I9 : 18 49 I~:A 38 1 : ?,4 96 80 0 : 20 100 U 17 0 : 12 100 48 0 : 56 I0O

* B r o o d 25-~rror in } t o w a r d (19,t0), "~ B r o o d 95-- t 'm.aa le DIB ?

produced broods with similar sex ratios in both years. Of these fifteen femMes, six were amphogenies--females BD, BG, FB, FG, JB and J D three were arrlTenogenics--fema]es ]3]~, CD and 7EAH; and six were

I f . W, I4]owxg~) 14I

.~helygenios~females CBJ, FA, FC, FF, KA and U. Females A~ and DE, also probably show no changes. Five females, however, do appear tO have broods in the second year which have different sex ratios from ~hose found in the first year. In m~e case~female DB---there is a small possibiIi~y of a clerical mistake in recording whether ]~rood 95 did come from .this female: Female AJ produced broods containing 88 azad 0 °/o of females in the {rst a~d second years respectively, and female AB (a siseer of female AJ) broods conbaimng 31 and 2~/o of females in firs±. and second years respectively. It is iz~teresting to note that the change is for a female to become more arrhenogenic as she grows o]der (of. Vandel's results), Female BN, however, appears to be more the]ygenic in her second, year ~han in her first, and female FD also changes fro.m an amphogenie in her first year to a thelygm~ic in her second. TJaus the results in Table 4 suggest that, while mos~ females do no~ cha~ge with age in the types of broods wkich they produce, there are others which have broods with different sex ratios in successive years.

I n Trichoniseus Vandel. (1938) fotmd females wkbh produced some broods showing d~elygeeie characteristics and odzer broods showing

.arrhe~aogenic characteristics. Such females are called allelogenics by gandel.

~II..T~E INHZI~.ITANCE 01,' ~IOlgOGENN-AND ANP3KOGENht

As has been previously stated, ~he-maIe parent does not appear to ha.re any effect on the constitution of a brood. In giving the results in this part, of the present paper, therefore, the male parent of the various broods is not give n inthe tables. The male parent mig~at, however, affect the type of daughters produced. The data on the inheritance of monotony m.~d amphoge~ty so far obtai~ed are of ~o nee for considering tNs sug- gestion. In d.iscllssil~g the results it J.s convenient to classify broods ia the w~y shown below :

C!onstit~$io~ of brood

3'Iore {hun 85 % females; less gha~x 15 % males S~-60 % fhm a.les ; 1.,5 40 % males 6040 % £emales; 40-60 % males 4Q-15 % females; 60-85% males Less th~m 15 % fem~tes; more ~han 85 % male,s

Type of female

Strong tb elygenic Weak thelygenie Amp~ogenie Wea,k arrhenogenie Strong arrhesogenie

In ~he tables the foilowi~.g nomenclatuze is ~lsed : F for strong {he].y- genic~ (~) for weak thdygenic, A for amphogem.c, (M) {or weal< arrheno- genie a,nd M for strong arrhenogenic.

It must also be remembered th~b the ]?erce_~J.tage of one sex in a brood as given in ~he tables has a large s~auda.rd error; th~.s the standard error for an am.piXogenic brood of forty animMs is ~l.bout; 8 ~/o and[ for brood of eighty animals about 5-6 %. _Similarly, the following hroods do not differ s:igdfica,~dy from beiJ_~g amphogenics (P = 0-05 ]evel), 8:2, 1¢:6, 90:I0, 26:1~., 31:1.9 and. 59:41.

148 The genetics of Arm~tdJllid.ium vulg~re Lakr.

(l) Descenda.,~t~ of tMl99en'io jbnale A Female A w a s a thelygenie female el)rained in a collection--she pro-

duced only cue brood which eonsJ.sted of 1 c?: 36 $$. As ~s shown in Table 5, however, not one of her ~welve daughters was a s'trong thely

Table 5. Desce,~z&~nts of femcde A Female A .< m~fe B produced brood 1 (1 d : 3 6 0 9 ; ~nimals YJA to ]tV)

ConsLitution of brood No. of c ~' , Tyl)e of

Female brood, d d : $$ % ~9 "# % l'em~le ]30 27 36 : 17 32 ±6.4 (M) BD 28 +90 3s : 67 64 ± 3 - 8 (dT) IBF 94: 23 ; 3 12 --6-, t M 7~Cq' 3 I +32-,'--122 16 ; 20 56 ±8-3 A .BIt 96 6B : 3 5 -J-2-7 3 f ]3K 33 + 1 1 8 50 : 0 0 - 2 - - ~'~'f B k [ 60 39 : 44 53 :h5.5 A B,xl 34 + t27 60 : 35 37 ~ 5 - 0 (i l l) :Be 39 22 : 1-t 39 ±8-1 ( M ) ~ P 109 t3 : 18 58 ±S .9 A ]3Q 99 6 : 25 81 ± % 0 (F) _BV 101 42 : 24 36 +6-0 (J]t)

I,e. female A prod~Lced B weak thelygeni% 3 ~mphogeuie, 4 weak mrrhenogenie and 3 strong arrhenoge!do daughtersJ

genie; three of her' daughters (BF, BI-I and BK) were strong arrheno- genies, four (BO, BN, BO and BV) were we~k arx-henegenics, three (BC4-, BN and BP) were amphogenie s and two (BD and BQ) were weak thelygenics. These results do not sllpport any. simple scheme of cyto- plasmic iuheritance of monogeny, and it was these results wh.ieh suggested the genetic scheme given in Table XIt of Howard (1940).

(2) Descendants of thelygs~.ic fe'mdes 6'B c~8 CO

A.s is shown in Tables 6 and 7, tl~e two' strong thelygenie females CB and CC were b o t h members of the same brood; while another female of this brood, femate. CD, was a strong arrhenogenio. The sons of female CD were mated with the daughters of females CB and COw, bus the granddaughters of females CB and CO (females EF, EG, OD to GJ and EL) are to a certain extent inbred.

Of the sixteen daughlers of females CB aiad CO, nine were strong thelygenics, %ur weak ~helygenies, one an amphogeni% one a weak arrhenogenie and one a strong aerhenogenie. Thelygeny does in this ease, therefore, appear 50 be handed on by a female to a majority of her daughters. Two types of gral~ddaughters of females CB and CO were examined--the daughters of strong thelygenie broods and the danght.e:rs of other types of broods. Of the seven, daughters of strong t.helygenie fem~-Lles, five were strong thelygemes, one an anapS.oge::io and one a.:: arrhenogenic (females EF, EG and GD to Git). Of the females :from other than strong thelygenic broods (fern.ales ]~K to }IN an.d FL), one was a weak thelygei£e, one an amphogenic and t, wo iveak arrhenogenics. I~ is unfortunate that more broods were no~ obtained from similar females, Nevertheless, the results do confirm the suggestion that in the

H. YV. HOWARD 149

deseendan%s of females CB and-CO thelygenio females do produce a majoi'ity of ~helygenic daughters, and ~hey do also suggest tha~ the

Table 6. " Dssce,~zdants of fe.maZes CB and CO

o E x ? c~ produced brood 4 (1 c~ : 4 ?~ ; animals C,A to _CD). 9 0]~ :<'c~ AL produced brood 29 (1 d : 37 ~2); ~nimals CIBA to C]3IQ. o CO x .J AL produced brood 30 (0 ~ : 25 o~; animals @CA to CCJ). 9 CD x d' AL produced brood 35 (64 d'd ' : 0 2; animMs 0DA ±.o CDG).

ConstiSution of brood No. of : ~" -, Type of

Female brood ~g.: o~ % co s % female

CBA 87 1 : 40 98 ± ~.2 P CBB t16 + 130 16 : 51 76 ± 5.1 (F) 0JBC 93 38 : 76 67 4- 4-4 (E) CBD 123 7 : 0 0 ~ ' - - M CBE 110 2 : I0 83 ±10-9 (2') O]~G 107 0 : 7 i00 ±-- F C:gJ 88+167 3 : 39 92 - - 4 -2 . 2

CBI,2 t06 2 : 22 92 ~ 5-5 2

I.e. 4 s~rong thelygerdes, 3 weak thelygenics, and 1 s~rong arrhenogenie.

~CA 120 I : 3G 98 -- 2"3- ~' CCC 97 0 : 22 I00 _ _ - F OCD I02+132. ] : 89 99 ± 1.0 /~ CCE 1 0 4 0 : 12 100 k iV CCF 115 18 : 9 33 -F 9 4 (3f} CCG 108 12 : 28 70 ± 7-3 (2) C C ~ 117+129 38 : 44 54 =I: 4-9 A CCJ 89 3 : 23 88 -F 6-4 .F

I .e. 5 s t rong thetygenics, 1 weak %helygenie, I amphogenic and 1 weak arrhenogenie.

Total : 9 s t rong thelygenies, 4 weak "thelygehies, I amphogenie, I weak arrhenogenic and 1 strong arrhenogenic.

9 C]~A >:d' ODE produced b lvod 87 (1 d : 40 oo; animals EC to EK) . 9 C:BJ × d ODG produced brood 88 (I c~ : 32 99; animals GO to GN}. ?_ CCF >:d ODD produced brood 115 (18 ~ ' : 9 '...q~ ; animals H,J to HIK). o CCG x d @DB produced brood 103 (12 6'~ : 28 9~; animals F I t to r L ) .

Consti tut ion of brood No. of r ~ a Type of

]female brood &ft.. ~O0. % O0.,.~. s % female

.EF 148 0 : 6 100 _+ F E G 1:55 3 : .'.50 94 ± 3.3

GD 150 0 : 11 10t~ d - - - 1 '~ £41f 100 0 : 7 100 ~ : - - F GG 154 2 : 15 8.q ± 7-9 F OI-1 ].$0 22 : 2I 49 ± 7.5 -1 (4J 168 6 : I 14- t:13-2 2]]

H I i 165 36 : 10 22, -I- 6-1 (z?f) I-IL 164' 4 :.1I 73 ±i 1.4 (F) I'IM 169 14 : 12 4(J ~ 9.8 A.

iT]] 149 15 : 5 25 ~ 9"7 (/if)

.~ J 3 J produced I.e. shelygenie o CBA produced :2 gbclygenic daughgers; thelyge~dc ? (~ • "3 %helvrgen[e, 1 a.n~pbogenie and 1 a.rrheJmgenie daughgers: weak arrhsuogenie ~q (JOF produee~l 1 weak ar,'benogesfic, 1 a.mpbogesfie'aud i weak tbe~vkcnic daugh.~ers~ and weak %he]ygenie o CCG produced 1 weak arrhenogenie da.ughter.

non-st:song thelygenic daughters of th.elygenic fema,Ie,s differ gon.e~icMly from the ,s~rong thelygelfie da,[~ghteJ.'S. Thus not o~e of ~he daughters of a non-strmag %h.elygenlc femMe i,s a, strong thelygenJe.

150 The genetics" of A r m a d i l l i d i u m vu] .gare Latr.

Table 7. Descenda,.nts of females CB and CC (see a, lso Table 6)

(9 CBB ( [6 ~ : 51 99) ~.~. E$ ' (0 c~ : 6 99) /?CBA (ld :4o7-~) ~ {gE6'..(ad:5oQg) | 9 C.BO (38 ,~d : 76 ¢o}

( ~ a'9°)-+ lgCBF,(q&?:1099) /961F(0d~:7-%9) 9 C3BJ (3 d ' g : 39 99) ~- J, 9 GG (2d": 15 99)

[ ,? C.B:K (2 fig : 29 '_{o~ ) I 9 el i (2~ ~d : el 9.9) k9 CJ3G (0 o ~ : 7 9~) ' [ ~ (~J (6 ,:~c~ : 1 9)

9 o o a (1 e~ : 36 99) i ÷ C O O ( o - ~ 9 . )

o ~, {~ ~: 4: ?9) ~. / ' . ; col) (~ j : 89 -99) oC.C(O~ ' 5 ~ ' o ) o ~ ,~, ~. ooo " HI( " ~-I000 !.~ C.CE (0 ,-~. 1 . _,..,.) [ $ (3~ a , ~ . -,--,.)

• OCCF 18 ~ - 9 ° o = oI-IS 4 5 ' 3 - 1 1 9 o) -,- ( oo-.+~) .- { . . . . ( . . . . -,- 9 CC]![ (38 gd~ : &iih?-) 1 9 ]-[-.'X (1:~ rid' : 12 °~) 9 COd (3 dc~ : B3 ~??) .9(.,0G(1~5,3 ~8~T) ~ e F L ( l o o o . a ~ ¥ )

' 9 CD (90 d,2 : 0 '~) -+ ,3,3 C ] ) A "Go ODC4.

(3) Descendants cf t/~,elygen,ic j'e,s~ale, DA

Of the eigh~ d~ugh~ers of the stro~g thelygenic femdte DA, seven are strong thelygenics and erie a weak thelyge~ic (see Table 8). Also of The four daughters of bhe strong ~helygenic femMe DA£' (hersdf a &ughter of female DA), three are strong ~helygenies and one an ampho- genie. These results certainly suggest tha t thelygeny is t ransmitted by a female to nearly all her daughters either in the cytoplasm or in the Y-chromosome.

Table 8. Desee.nda~.zts of female DA $ ] )A × ~ SB p roduced brood 4:7 (0c~ : 30 ~2; animMs ] )AA *o ] )AH) . $ D A F × g D B B produced brebd 74 (2 ~ : 4-2 $$; animals D~P to DN).

Cons t i t u t i on of brood !Vemale No . of , *" , T y p e of paten% brood &? : .o 9 - % ~ ~ % female

DAA - 81 0 : 13 I00 ~__ i~ DAB 108 3 : 78 96 - :2-2 2~ DAC 91 0 : 31 t 0 0 ! - F D A D 126 7 : 49 88 --4"4: I)AE 92" 0 : 21 I00 __2-- F D A F 74 2 : 4-2 95 --3-2 av D A ~ 98 11 : 23 68 -A-8'2 (P) DAI-I. ].25 0 : 29 100 ± - ff

])IT 1.56 8 : 6 43 =13.f i A D X 151 0 : 83 I00 ±- 7P D~[ 159 0 : 16 100 ± - - F Dlg t61 0 : 15 I00 ±- Y

(.i)' Desce.~~dents of arr/ze,noyen,ie fe'm, cde AB The. strong arrhenogenic female AB was a &ughiev of female C (a

weak thdyge.nio femMe; 7 ~ : 1¢ 90). Also daughters of female Q (see Table 9) were female AF (a weak thelygenic), female M (a strong thely- genie in one year and g strong arrhenogenio in the next, see Table 4) and fem£1e CE (a strong thelygenio): ~emale AB also appears to become more arrhenogenic as she grows older, see TaMe :4-.

Of tl~e six daughters of female AB, three are strong arrhenogenies, one a,n amphogenic and ~wo strong thelyge~ics (see Table 9). Thus a strong s, rrhenogenie female produces mainly s{rong monotonic daughters,

If . W. Howa~oD 151

bu~ these monogenie da.ngh%ers include both strong thelygeMos and sh-ong arrhenogenics.

As has been previously mentioned, ¥a~del (1938) found ~hat in Tricho~%sc~s thelygeMe females often produced mainly m.'rhenogemc

Table 9. Descends'ms of female AB C x 2$ produced brood 2 (4~c~ : 9 oo; animals AB to AN). C x ~ ' B produced brood 7 (3 cf~c~ : 5 $~; animals ON to C~) .

$ A B x ~ B pl'o~iuced brood 8 (22 d d : 9 99.; animals NO to NO). $AB x g AZt produced brood 25 (40 dc~ : l o; ~nimMs ZA ~nd ZB).

Consti tut ion of brood :Female _No. of r-- ........ ~ ..... , T )~e of pa r en t brood dc~ : 83 % o~ s % female

A_B 8 +25 62 : 10 14 ±4.1 3'/ A~7 10+49 19 : 46 71 ~5.6 [~] AJ* 2 6 + 4 4 + 6 9 17 : 57 77 =1=4.9 (F) CE 43 4 : 39 91 ::t=4.9

t~2E 79 20 : 2 9 ±8 .1 z~I tAN 77 ii : 0 0 _- 3f K J 133 14 : 0 0 i - - ~I Kl'vI 91 0 : 15 100 4. I iO~ 64 11 : 15 58 =I=9-7 A ZB 124 1 : 8 89 =t=9"9 F

* 9 A J - - s e e Table 4, part, ieu]arly brood 69 (9 £6" : 0 ?). + 9 K O - - b r o o d 64, male pa ren t was a French anlmal. Of the 6 daughters of female A]3, 8 ~rere strong arrhenogenies, I a.n amphogenic a.nd

2 s t rong thelygenics.

daughters. This change from one type of monogeny to the other is very hard ~o explab. It may, howeverj be of importance $o note that it can also take place in the same female, e.g. female AJ above.

(5) Descendc~ts of amphogeni~ femde NA

Brood 24 (46 c?~ : 47 09) from female EA was chosen for inbreeding in an attempt to obtMn lines breeding true for amphogeny. It was found, however (see Table 10), that brood 24 females were either arrhenoo

Table 10. Desce,~l, da.rd, s ojV"e~J~a~e EA

EA >" d S:B produced brood 24 (46 dc~ : 47 _~!~:; animMs EA-4 to GAP). E A F x ~ EAE produced brood 73 (4 d'~ : 17 ~9 ; a.nima.ls AP to A:R.).

Constitutinn of brood FcmMe [No. of r ~ ' ~ - - , Type of pa,renb, brood g'd' .- oo~ o,zo ~"~-~ s % fcma.le

EA]3 85 .5 : 0 0 - . : - - ~1I EAF 73 4 ." !7 81 i 8 - 6 (1#) NAG 70 0 : 16 100 ~ - - - ~' EAI-I 83 + 1.58 1,4 : 2 13 ±8-4 2If

A:P* t34 0 : 28 100 -- .F A~, ]36 0 ; ].0 100 - - .E

* 9 AP was a x~dli~e m u t a n t fcmMe.

genies or t~e!ygenies. I t was a,lso t'onud ffhat two daughters of one of the ))rood 2,I thelygenie :[emale,s were strong thelygenics. There is th~s no don])~ t].mt the a(ppare~lt].y amphogeme femMe ]~A produced daugh~ers wh.[ch were gmteticalIy monogeuic, One possible explanation of this resuR is tha, t female gA, Mthough art amphogenie herself, was a daughter of a monogenic female (of. th:e results of Rhea,des (1933) on male sterilRy

152 The genetics of Axmad~il] idium v u l g a t e Latr.

in maize; these resalts are discussed lal;er in this )a]?er). Vandel (1938) also describes a type of female which he calls a mix~. Mixts produce ;.~mph.ogenic broods but are ghe descendants of monogeni.c :["ema.les and ~hemselves produce monogenic daugh%rs.

(6) De.~cs,;adants qi" 4m,pl,.oge'~?,ic,fe'mde !r~ Descendants of the ~zmphogenie female FB have been inbred in a

seeoad ~gtempt ~.o obtain lines breeding true ibr ~mtShogeny. The results are shown in Table 11. I t is unfortu~.al;e that the broods tl'om the

T~ble 1i. Des~snda~vts o/,7%~.ale FP~ ~i! JP.lg x ?d SB pr<iduced bi'ood 51 (~9.'[.@~ ~ : lO1 ~.~). ? FB, no 6' since brood 51, produeil.d brood ~1 (34 c~d : :32 9°) , ~2 FB, no 3 ~ sheet brood 51, produced brood 63 (8 d~,6 ' : 12 oo)

Tota l : 136 d ~ ' : 145 O?.

Consti ~utiox~ of brood

Femt~Ic }~Me , ,~-~ No. of pa,.'cnt p a ~ e n t ~,~ : $o brood IF]3}~ ~BK 3 : 3 135 FJ3D F.BD l0 : S 137 F B E ]fTgO 5 : 6 ISg f fBF FBC 0': 2 139" FJ3G FBA 6 : 5 140" F~TI F]BA 8 : 9 I~I* FBX F~J :~ : 1 144 FBL F]~J 10 : 15 142 FB~I FBJ 7 : 7 143

Total 49 : 56

2knimMs F B A to D't~I~£ were al l members of brood 63. * ]Broods 139, t 40 and 141, wh ich were MI f rom b l~ck females × g l a c k males, showed

segregat ions for bl;~ek v, whi~e b o d y colour. I t t h u s seems t h a t e i ther female t0B or t h e rome pa.rent of b rood 63 was he tcrozygoue for recess ive genes for whRe body eotour.

brood 63 females are so small. There is, however, some indication tha t all the daughters of the amphoge~ic female FB might be amphogenics. I f female FB and her daughters are ~rue amphogenics, it is.interesting to note that there maY be a small excess of females, ~he supposed heterozygous sex, over males in amphogenio broods.

(7) Summary a,nd discussion The results given in §§ 1-6 of Part I I I of this paper may be more or

less summarized as:

(~) 9 A (s%rong thelygenic) -~ 2 (F) + 3 A + 4 (M) + 3 M; (b) o @B and ~ gO (strong thelygenics) ÷ 9 77 +4 ( f ) + 1 A + 1 (M) + 1 M;

@ CBA and ? @BJ (stroag thelygenios) ~. 5 F+l 1 + 1 M; (c) ~ DA and $ DAF (strong ~helygenics) ~ I0 ~v + 1 (F) + 1 A ; (el) ~ AB (strongarrhenogenic) ~- 3 M+I A +2 F; (e) 2 EA. (amphogenio) ~- 1 7?+ 1 (F) +2 i]~f; (:f) o FB (amph.ogenie) ~ 7 A ;

where .F=strong thelygenie, A=amphogenic~and M=strong ~rrkeno- genic, etc. Thus in ~wo cases, (b) and (e)~ ~he results do suggest ~hat a thelygenic :female produces msgnly thelyg,enie daughters and in another

I-t. W. l i e w - a ~ ].53

ease, (f), that an amphogeni.c female produces, mainly a.mphogenie d~ughters. Saeh results would be expected if the i~heritan~e of thdygeny and. amphogeny was cytoplasmic (or if due to factors in the Y-chromo some). The other cases, particularly (#}, appear at firs~ sight to disprove ~he hypothesis of cytoplasmic i~heritance of monogeny and amphegeny. However, if we examine the da tao f Rhoades (1933) on the inheritance of male-sterility in maize--this is one of ~he most ~horoughly inves~sigated cases of cytoplasmic inheritance--we see that the ir}egNarities in the 2Tmag£1idi '~z results would not be ~mexl?ected if the inLeritance of monogeny and amphogeny was eytoplasmie. Thus l~hoades found that, of eleven cultures f~'om baekcrosses of male-sterfle]nclividuals with un related normal iines, six cultures contained male steriles only and five cultures, both male steriles and normals. Also when normal plants from these mixed cattures were bred from they produced some cultures eon- ba,ining male steriles only, other cultures containing both normals and male steriles and others oentaining normal plants oNy.

On the other hand, it must be reeog~ized that the results given in this paper clo not prove that amphogeny and monogeny are inherited eytoplgsmicallyin/zr~edil~idi~t~m Considerable farther work is obviously required on this rather diitbult proNem. One of the best lines of g~taok weald appear to be to tes~ whether ~ke.male parent has any effect on ~b.e type of daughters produced. Before this can be done, howe-get, i~ is necessary .to have lines which are breeding more or less ~rue for ampJ~ogeny and monogeny.

(1) 2]/fo~oge~y ~.~ cm o~tbreed.i~..y v~ed~.,m:,~

One effect o:f monotony is that ig restricts inbreeding ; thus, brol:her- sister ]::a~ing canno~ take place in a thelygen:c brood sinee s:~eh ])roods contm~in no males. Also the da~@aters of a t]:~elTgenic female have no male coush~s on the materna.] side i:f thelygenie :[e~ja, les always produce thely- genies a, nd are themselves pr~)dueed only by thelygenics. Monotony is dins an outbreeding mechanism analogo~l.s to [,hose found in the higher plants and lanai (Nather, 1940, 19~12). It is of interest 1,o note in this eon.- nexion. ~hat natural l_,al?ulations of A~'.m,~,giggig.imm do contain recognizably different gene~icai l)y]?es in quite high percentages (see Table NII I of Howard, ] 9~1:0). T]~e,~e iuel.~de, the d.omina~t red :form. a,nd two dominant sex-lhnibed forms, types C and D. geeessive genes are also ap]?aready present in the heterozygous eondi~io.la--some evidence has been obtained :for two reeessives fo:c white body colot:~r (the ratios for black : white in families 139, 140 and I41 of Table 1I appear to be 9 : 7 and not .3 : 1) a.nd also of aaohher for yellow body co]our.

An. Arqr~,(~d,~7~id'h~'m population containing only thetygex~ie and am.pho- sonic females and males resembles to a certain extent the gynodioecions

154 Tl~e ge~etics o f ' ~ 'mad i t ] i d inm vu lga re Latr .

species of flowering plants (see Lewis, 1.94:1) in which the m~fle-sterite plants must be pollinated by the her.maphrodites while the herma- phrodites may be either selfed or pollinated by other herr.naphrodites.

T,'~ble 12 (1/ Drosophila.

(a) NormM tomes: X Y - + 50% X spe rms+50% Y sperms. (b) Sex-ratio males: X F Y -+- 1.00% X -~ sperms.

(2) Ar~eadillidium (~ene fe~ tAel:qgeny on Y-cAromsss'me), (a) _Amphog, el~e . . . . . . femMes" NY ~> 50 % "r eggs +50 %., Y eggs. (b) Thelygenio females: X Y*v ~- 100 % YF eggs.

(3) ArmadJllkli~m (W~o2las~Mc deterszO~atibn of thdyge~V). . . . . . . . . v . . . . . . . {oO Yo 6 (.X) .~,~s -~ mMe~.

(a) Ampnogemc inmates, c (~k i j ~ 150 % C ~v (Y) eggs ~+ femMes, (b) Thely.gerdc females: 6 'F (XY) ~- 100 % 6 'F (Y) eggs ~- femMes 50 % of the Ot¢ cytopIasm will be lost since the sperms fl'om the males carry no eytoplasm. No 6 'z'~ cytoplasm will be lost in ~his ~vgLy shies the ghelygenic females produce no males..

(4:) G~nodioecio.~a species of fle~ver'ing 21a'n~ (i:yloplasm.~c determine*io,n of ,male sterility)..

(a} t{enna,phrodites: 6 '-'v (AA) ~- 100% ovules U *v (A), (3) 3'rule sterites: 0 F (AA) ~- 100 % ovtdes 6 'F (A).

]?'or fu~I description, see texe.

Similarly, all the daughters of thelygsnic females have to mate With ma.les from amphogenie broods while the danghters of amphogenic females may mate wil,li sigher, their brother.s or with males from other amphoge~ic broods.

(2) 21~e effes~ of ,mo~.ojeng s~ ~ez r~tios in ~.~at~ral 2op~lag.io,ns

Monogeny, particularly thelygeny, may have a very large effect on ~he sex ratio in natm'al popuIations. Thus if we consider the Ample ease Ca whi?h ghelygenio females produce only ~helygenio daughters and amphogenie females only ampgogenle daughters, and if in addition i~ is assumed bhat, ~he broods from thelygenie females are of the same size as broods from amphogenies and that the daughters of thetygenics have ~he same viability as the daughters of amphogenics, then Wen random mating in a large popul~ton it is obvions tha t ~helygenie cytoplasm (or thelygenic Y-chromosomes) will increase twice as fast as amphogenie ey~0plasm (or amphogenic Yochromosomes). This process is shown in Table 12. This means ~hat ~he female population wonld soon consist entirely of thelygenic females and also that there wo~fld soon be no males in the population. The sex-ratio case in DrosoIoldlc~ (see Dobzhansky, 1.939, p. 365) has a similar effect on the constitution of a pop,darien. This case is also shown briefly in Table 12. In a gyaodioecions species of flowering p]:an~,- however, given, eclaal seed produ.ctio~ by the male s~eriles and hermaphrodi~es, the re% of increase of male-ster.ile cyto- plasm is ectnal to that of normal cytoplasm (see Table 12). Also as pointed ou~ by Lewis (1941), ~he per.oen~age of male steriles will cease to increase when t}leir higher viability (due go ontbr.eeding) is conntered by their r.educed reproduction rs.~e due ~o a shortage of pol!en (it is

It. W. tIOWARD ]55

assumed ihat the her]naph~'odites will be more efficiently pollinated than the male s~eriles under such conditions). Similar. conditions, i.e. a shortage of ntales, are not likely to produce the same effect in animals-- there is no reason for believing that in woodlice a male would tend to mate more often with amphogenic i%males than with thelygenics.

In _i~'.mad~[~idium and. in T,r,ic~.oniseus, however, the situation is not so simple as we have so far suggested in this discussion. Thus in Ar~nadf~- lidiu~n thelygenie females do not produce all thelyge]ic daughters, a n d in Trichoniscus thelygenic females produce abdut one-half ~helygenie daughters and one-half arrhenogenic daughters. The effects of these complications on the constitution of popu}.a%ions are considered below.

(3) Possibl, e stable types of ~)o2~Zat.io~s

The first type of population considered is that in which a.mphogenic females produce only a.mphogemo daughters and in which thelygenic females produce one-hMf arrhenogeaic'and one-half %helygenic daughters. It is shown in Table i3 ~hat such a population is s~able. Such populations

Table 13

(e) 2~phogs~,ics, thslyge.n.ies a~d c~.rrhe.noge~ic& Amphogerdc females produce 50 % males + 50 % femMes. The]ygerdc females produce 50 % thelygen~es + 50 % arrhenogenies.

Such a population is sta.ble as is shown below : 30 amphogeNc females - ~ 30 amphogenic females

-~ 30 m~les 60 males I0 arrhenogenie females --~ 20 males

• 10 arrhenogenic, femMes I0 t,helygen~e females ~ i0 ~helygelfic females

(~) ThetggsTdcs and ar.rhenogs~dcs .No a.mphoge~ic,s. Thelygenic f6mMes produce 50 % ghelygcnies + 50 % 'arrhenogenics.

Such a population is also sty.hie: 50 ma!e~ 25 a.rrheuogenic females - - ~ 50 maI~s

25 a.rrbenogerfie females 25 thelv~crde females ~ ~5 o . . . . . ~ %helvgenic l%ma.lcs

do appear to occur in. Tric/~o'J~iscus. Thus Va,ndel (I.9:38) found that of eighgyMght :mm.~ogenic females obtained from collectiou.s tbrty-one were a, rrhenoge~ics a.nd thir ty-two thelygenics (the other fifteen, anhnals con- sisted of thirteen a, llelogenics a,nd. two mixts). Also of fifty-two daughters of perfect the]ygenie females twenty-seven were arrhenogenies aud sixteen. th.elygenies (the other nine were allelogemes aud mixts). A.s is shown in, par t (b) of Table 13 ifi is also possible to imagine a population in which there are no am])hogenic :females. Var, del did find populations with under

. , ~ ( • 50 ~/o of i)l~e :[%males of the a mphogenic type. Koreover, ~ c~,are cofro)~h,i~r~ is an example of a,n a,nima] which has no anJphogenic females but o~]y 50 c~/o of t]lelyge~ri.es a~td" 50 ~ of a,rrhenoge~ics. In this- animal also (N[etz, 1938) thetygenic;s do prod~:tce 500//o theJygenie and 50}/0 arrheno- gefiic da.uglreers. In 2richo,ni~c,~, however, Va.ndel (1938) fonud that all the daughbers of one the].ygenic female might be thelygenies while all the

156 TI~e ge)teZfcs of sh'madill_i.dium vulga~re La~'.r.

danghters of another migihg be arrhenogenics. Thelygeni¢ femMes pro- d.uei~].g one-half thelygenics and one half arrhe~.ogenio daughters were not found.

The second type of popnlatior¢ to be considered is th~g in which amphogenie females produce only amphogenie daughters" and in which ~helygenio females ]?J:odnce some ~helygeni.o ~::d some amphogenie datighters. This case is considered in Table IDL As e, an be seen from ~hi.s

Table ],'~

_lasa,mlgfo.~s (a,) Amphegenies produce 50t}~ males + 50 o~ amphogetfie femrdes. (b) Thelygeaies prech~ce p [helygenie females : q ~ (1 - p ) aml?hegenie ±~m~les. (~) AmphogenJe and /helygenle broods ~t'e of the same size. Le. thelygetfie broods

cent, sin ~.wiee as Rtauy ii~mates a~s ampho~enie broods. (d) "fhe oft'spring of ampi~ogenie and thelyg~'~'~ic females have eqmd viabilJt, ies, T]~e~, i[ ,~ pOl?ulation cent.sing 2 e.helygeaic and 1 - F amphogenie fem~des, for equi-

iibrium eondi~lm~s between amphogenle and t, helygenie females

2l 2;' 17 ' 1 + ,Iv

from which we .tlnd tha~ T .. . . 2 "

Also m~ch apo t , ulatfon wl[1 eontaLu 1 - F ramies and l - F - [ 2 (1 -p) F +21)1~ females. females 1 ÷ f

Eenee the rat, io tors i aifimats B

15'creates ~ = ~ , VahI es of r

% ampho- % ghely . . . . . . . - - - J ' - - ~ Poptfla~ion genies genies ~ p .? % females/ total animals 100 0 0.50 0'50 50

90 10 0 . ~ 0-6~ 5~ 80 20 0.~0 0-60 60 70 30 0'35 0-65 65 60 ~0 0.30 0.70 70 60 50 0-25 0-75 75

4 0 60 0.20 0.80- 80 30 70 0.16 0-86 85 20 80 0.10 0-90 90 I0 90 0-05 0.95 95

0 100 0"00 t 0 0 t00

table a whole range of s[abte l~opala~ions a~e ioossibie depending upon ~he p~dportion of amphogenie daughtersproduced by thelygenl6 females. The application of~hese results to Ar~adiZ~idf~n~ populations is con- sidered in the n e w section.

(4) Armac[illictiunf po2z&ctfons I t ca.n be seen fi'om Table I5 that about one-beE of the females from

collections are amphogenics and one-half the]ygenlcs. These females, however, are not a rando m sample bu~ were in many oases chosen b e e a l l s e ~shey s h o w e d d i f f e r e n t c o ] o u r types. I~ c a n a l s o b e s e e n f r o m

T a b l e t..5 %hat n o a r r h e n o g e n i e f e m a l e s o c c u r r e d . A c e o r c l i n g t o T a b l e L i

a p o p u l a t i o ~ i c o n t a i n i n g 50 ~/o o f t h e l y g e n l e f e m a l e s , w o u l d l i e e x p e c t e d

to } l ave a b o u t 75 °/o o f f e m a l e s , a n d t h e t h e l y g e n i c f e m a l e s i n snob. a j ? o p u l a -

t i o n w o u l d b e e x p e c t e d t o p r o d u c e 3 t h e ] y g e n J e : 1 a m ] ? h o g e n i ¢ d a u g h t e r s

(assuming that ~he population is a st~ble one). The I)eroe~l%ages of female~ in a nnmber of popula[ions are given in Table 16. bios[ of ~he females

H. W. HOWA~<D 157

in Table 15 came Dora collections A-D. These fete" collec~Jons have a mean percentage of females of about 74 ~/o- Of the thelygenio females considered in Part III of this paper, females E and DA. came :from these

Table 15, Females fl'o~n cdteetio.ns Constitution

of brood D e s c r i p t i o n o f N a m e of No. of , . ~ -~ - -~ T y p e of

f ema le f ema le b r o o d ~ d ; f)O f ema le

B l a c k , fi)~Je 28 C 2 4 : 9 A . . . . E A 24 46 : 47 A . . . . F A 2 2 + 6 6 0 : 87 F . . . . FiB 5 i + 6 1 + 6 3 136 : 154 A. , , , , ]?'C, 5 2 + 6 2 9 : 1 7 ¢ .F ,, . , , F 1 ) . (see T~ble 4) 7 . . . . ~ 20 23 ; 29 A . . . . X A 3 8 + 8 0 ] : 44 _~ . . . . . U 1 7 + 4 8 0 : 8 8

V 52 89 : 41 A

. . . . ,JB 4.6 + 1 2 8 1 2 5 : 1 7 3 i J D 4 5 + 6 5 5 9 : 7 2 A

,, ;, F F 5 9 + 6 7 8:97 . . . . G A 37 0 : 13 F

JC 42 22 : 14 ~-i :Black, t y p f f D D A J7 0 : 30 F

. . . . D B (see T~ble 4) ? D D 50 5 ; 8 .-1

,, ' ,, D E 5 4 + 6 8 ~0 : 6 2 A Yet low F@'~ 1 1 ~ + 1 6 3 22.: it4 A

I,e, 11 amphogenies and g flhelygenies (also 9 ]?g) and o D]3}. * ~ FF. w a s h o m o z y g o n s fo r t~ype C. j" ~ ]PG-- t .he ye l low in th i s case might be a modi f i ed t y p e D.

Table 16. Sez 'ratios i~, wiI.d po2utations Cons~i6ntio~ of

col lect ion Oo]leet ion Pla.ee of f "~

no. eol.tce~,ion , Jd ' : ~ ? % 9~ i Pirsb wood o n @ogs 22 : 81 78 _]3 ~PrtEmpingt.o~t 17 ; 3i 65 C Fa.r w o o d c a (JoSs 1~ : 79 8._5 D N a d M g l e y ].t :2.'5 09 E F e n LDK.lol] 24 : 34 59 F "Universi ty ti~'~'z ]9 ; 23 55 10 W o r s t e d Iodgc 11 : 2] 56 i 1 FJrs~ wood on (}ogs ~! : 13 77 12 ]~irst w o o d on (clogs 10 : 19 66 l~l: Flea.m ] ) y k e 2:~ : 20 47 I ,.5 F u l b o m ' n 28 ; 53 85 J6 U n i v e r s i t y F a r i u ] 4 ; 16 S3 17 B o t a n i c C~ardens 8 : q 53 IS W e n d e n s A m b o t l : lS 58 19 ~Vende~as A m b o 69 : q~'~ 38 B0 W e n d e n s An-the 84 : 51 42 ~ t W e n d e u s A m b e .14 : 20 59 ;32. A b i n g t m , ~1 : 4:8 61 .28 [_Tniversii,,, ~ a r m 7 : fi0 74

:four popu].ations whi.le female }3 came Don: a popula,tlon aJ.ot given in Table 16. I t Js thus of some kfl,erest ~o note l;]:al; of the ~)we::t;pfour &~ughters of l)he @e]ygerde %.melee CB, 0C and DA, sixteen were strong

thelygenios.

158 T£e get,erich' o/Armedillidium vulgare Lat,r.

It will also be noted[ ~ha.~ only three of the populations in Table 16 show an excess of males alld in only two of these is there a large excess.

These flgr~res for A.rm.adiglidi'~tm population s are no~ very satisfac%ry and the assumptions made in the calculations in Table L'I- ~re also known to be only partially true--~!ms so account has been ~aken of arrhenogenic females or of amphogen.[c females which produce thelygenia daughters. Nevertheless, they do give some idea of the equi.librinm eond:il;ions in such populations. The calculations also show ~he significance of thely- genie females not breedbxg absolutely true for thelygen.y.

Tl~e small percentages of males in some populations suggests ~he importance of Imowing haw many females a single .male can impregnate in one yea, r. Under laboratory condit;i.ons this has been found Co be at ].east th:ree or four. i~ also appears ~h.at g single impregnation gives a female enough sperms for producing broods in two years.

I. Three types of fema].e are found in the woodlouse Ar.madfglid'l',~.~,,a v.~d.gare--an,phogenies which .pro&lee broods consisting of 50o/o males + 50 % females, ~helygen.ies which produce broods consisting nearly en- tirely of females, and arrhenogenics which produce broods consisting =early entirely of males.

2. }Ionogeny (thelygeny and arrhenogeny)is expldined on Va~del's hypothesis. Assuming that the females are the heterozygous sex (chro- mosomes X Y), it is suggested' that in monogenics segregation of {h.e sex chromosomes into the eggs and polar bodies is not random--all the eggs of a thelygenic female receive a Y-chromosome and Mt the eggs of an arrhmmgenio female an X-oMomosomv.

3. GeneticaI rabies show ttiat normal segregatio n of the autosomes ~akes place in the eggs of monogenic females a~ct that the eggs of such females do not develop parthenogenetically.

'*..In mos~ oases different broods from the same female have similar sex ra-~ios.

5. The inheritance of monogeny and amphogeny was studied in ~he descendants of four thelygenic females (~wo of them were sisters), of o~e arrhenogenic female .and of two amphogenic females. The resuRs support to a certain extent the sugges{ion that monogeny and amphogeny are inherited cytop!asmieaHy (or in the Y-chromosome). A tb.elygenic female may, however, produce amp]logenic daughters and an amphogenie female thelygenic daughters.

6. The effec~ of mon0geny on ehe composition of natural populations is considered. It is shown that thelygeny may'have a large effect on ~he sex ratios in populations, Nest 3rnzadd,~idi.~,~n populations contain more than 50% females and of these females about 50 % are ampho- genies and 50 % therygenics.

}I. W. I-IOWAl~I) 159

REFERENCES

DoBzt~sm~-, T. (1939). Experimental studies on gene~ics of freediving popml~tions of lProsophi~a..BioL t~.v. 14, 333-68.

I-IowA,9, H. W. {1940). The genetics of A~'madillidium vtdgare Latr. L A generM survey of the problems. J. Ge~et. 40, 83-103.

L ] ~ s , D. (1941). 3la]e sterility in ilatm',M popu]atidns of herniapkrodite plants. The equilibrium between females and herma.phrodRes to be expected with di~z 'ent types of inherltanee. ~Tew PhytoL 40, 56-63.

5;E~Tt~I{] X. (19~0). 0utbreed2ag and separation of the sexes. 2VatwrG Long., .:t45, ~8.~87.

~,L.~m~, X. (1949). Heterothalty as a.n outbreedLng rneeha,nism in f-angi. 2Vaturs, Land., i 4 9 , 54-6.

B~Tz, O. W: (I938). Cl~'omosome behaviom', h±erita~ee, and sex deSermkla~ion in Nciara. Amsr. ~Vat. 72, 485-520,

~ t o ~ s , 3{. N. (1:933). The eyl:oplaslrde inheritance of raM~ steriligy in Zsa Mays. o r. Get,st. 27, 71-93.

VAxD:~5, A. (i938). :geeherehes sur la sexmalit~ des isopodes. I I I . Le dgtermiaiszae 4u sexe et de la ~onog6n~e ehez Trichoniseus (~2i~on~scus) fproviseri~ts ic{.aeovitz~. Bull. bioU 72, 147-68.

~:n~°D~.Z~, A. (1939). Sur le mode de r@argRion des sexes ehea l'isopede terrestre, A~'madil~ic~ium vulgate (Lagr.). C.fL Aca.d. ScL, Paris, 208, ]050-52.

5r-~D]~5, _&. (194]), The genetids of sexuality in LerrestrG1 iSOlOOds. Prec. 7th Int. Gen. Congr. Edinb. pp. 308-7, :4_ugust 1939.