IM. A'l'l'] S 



i;\'PI,,\\A'l'|()N OK KKMUKS 



.'is 'I'hc iii('(li;iii .siiif.'icc (if .'111 ()v;u-i;in cj^fi; Iwcnty-four lioiirs hd'oic oviiljit ion, 

 (•111 in li.'iir (liroiitili IIk' l(inji;iii(i polar uxcs, ;i,ii(l i)hot()fi;rni)li(!(l hy I'cflcclcd litjlil . 

 X'-i- Tlic ccnl i;iM,iti'l)r;i (/'//.} is cliHtincI ly C'li'l Ik'I' iroiri the right hand end of Ihc 

 ioiifj; axis, the end, natrudy, which was directed posteriorly ('(doacally') when Ihe; 

 liird was opcuictl. The ii('(d< of th(! latobra extends uj) towards the Ijlastodise at 

 I lie pcrii)hery. ('oiiip.iic uilli diagram 2 E (in wliieh the concentric layers of 

 yoll< lire not represented). 



'.',U A photogr.'ipii siniii.Mr to I he onesliown in fig. .'JS, from an oviducnl egg taken 

 Iwenly-six hours after ferf iliz.-it ion, showing the common tyf)e of latehra of ovi- 

 diical eggs. 'I'he section did not cwi. the hhistodisfr exactly in the center and so 

 I he i nf iindilnil;! r e\l ension of t he l;i I el)i;i(loes not .'i ppe;u', hut- it is i ndic;i t ed hy t he 

 arrangement of the surrounding layers of yolk. When this is considered and 

 allow.'ince is made for- the; (iracking of the yolk at the infundibular end, the center 

 of t he latelna is '2 mm. lu-arer this end of the long axis, 'i'he hole iii the yolk at 

 t he right was tn;iilc liy t he pin i n si •!■ ted to mai'k t he cloacal end of I lie egg when it, 

 was obtained. 



40 A photograph of a p.aras.agit t ;d section of the bLaslodisc of an oocyte, 17. S 

 x 10.!) X lli.!t mm,, taken .about liti hours before; ovulation, fixed in sublimate- 

 acetic and stained with neutral gentian. Leitz obj. .'{, X 5(). The 'wedge' gran- 

 ules lirdf/.) for-m ,a collar' around and tapering tow.aid t hegernunal vesicle ((/.p.), 

 which is immedi.ately suiT'ounde<| by the polar granules, {pjj.). o.r/. and o./>. mark 

 t he .anterior .and posterior iTi.argins of t lie oiilei' peribl.ast ic zone of t he blastodisc. 

 II .\ i)liotogra,i)h of ;i par.asagilt-al section of ,aii egg with the first: ch^avage 

 spindle formed, taken from t he enliji-iice to t he shell gl.aiid at 1 1 cm., lixed in siib- 

 limate-acet ic and stained with neutral geidiaii. Leit/obj. .'i, X IN. The wedge 

 {ivilij.) is clearly delirKMl posteriorly and absents anteriorly, 'i'he peribl.astic ring, 

 {phl.r.) is of the diffuse type. 



42 Siirf.a-c(^ view of tiu; bhistodisi- of an oo(\yl:(! removed from its follich; about 

 forty-five hours before ovul.ation would have (x^curred norm.ally. A copy of a 

 <lrawing m.ade from I lie living ovum. X H). At I he cent(u- is the germinal v(>sicle 

 U/.v.), wilJi 1\h' mn-rowopa(pie (white) zone of polar granules ((;f. (ig. 10, p.i/.) . The 

 segmental disc is circular and appears light ; at its outer margin tlu; t r:insi)aretit 

 (dark) inner p(M-il)last ic zone ii .phi.) is different iat ing. At t he outer margin of t he 

 periblast a,re light spots wliicli icpresenl groups of peiiblastic gr.aiiules. 'i'hese 

 liav(! not. yet, appear-ed ariterioi'ly at <t.o. The a-iitero-posterior axis iiuii(;aied by 

 this differtmce in the struct rire of the periblast formed an angle of ().'") to 70 de- 

 grees to I, he long axis of I he oocyte. 



4;{ Thesiirf.ace view <if the bl.isl odisc of a feit ili/.ed egg taken from the infun- 

 dibular' t liird of t he oviduct and dr.avvn aft(M' one arul one ([uart-er hour's of irrcii- 

 ba,t ion. Abagniiied ten t imes. ,\ copy of one of a sei'ies of dr'awings of t he li\'ing 

 (>gg showing the I'oirii.it ion of the |)eribl;isl ic I'ing (phl.r.) (vL lig. .'35). 



328 



