mi. I'):-' \<.r.. 





,v herons in the case of the 1 the lirst plane of dflfl 



through to the opposite pole, in the GM6 "t the Hen's egg it divides 



onlv the grrm-di>e into two similar segments, which like two he,.U 



Mj)on the undivided \olk-m:iss with a broad base, by means of 

 which t-hcv still ha\ea physical connection with each other. Soon 

 this, theie is formed a second vertical furrow, which crosses tin- lir-t 

 at right angles, and likewise remains limited to the germ-disc, which 

 fe now divided into four segments (fig. l\'.\ !'}. 



Knch f the four segments is again divided into halves by a radhl 

 furrow. The segments thus formed correspond to sectors, which 

 u.eet in the centre of the germ-disc with pointed ends, und have 



a b I 



fig. 34. Section through the germ-disc of the Hen s egg during the later stages of segmentation 



i;u IMI-K. 



Tin- siTtioii. \\liit-h rf]n.-.--iit> iathT ni<>i- th.in h;ilt' tlc lurailth of tin- Hu-t<xliTin (tin- initldlo 



liiu- i.-at '>. ~h..\vs tli:it t v f UM MttfMe md of UMoantraol tin- iliac are smallei 



than tlm.-e U-luw ^tinl t.. \\.n.l tin- p<-i iplnM \ . At tin- l>.mliT tln-y are still very large. One of 

 rli.- l.itti-r i> imli.'.-it.'.l at . 



i.liiT.-il >-fll ; /i. l.ir^t-r i-i-ll- "f tin- I.iuiT i.i\. i- ; . iniiUlle line of the bLututlfim : 

 .. IxnuuJai y l>ct\\.-eii the blastoderm ami the white yc.lk 



their broad ends turned toward the periphery. The apex \ e u-h t 

 the >e^u:<-iit> i- then cut oft* by a cross furrow, i.e., by one which i> 



parallel to the e juator of the egg (fig. 33 C), in COllseipieUi e of which 

 there are formed Minller central ('^ and l-irger peiiphn-al (!) seg- 

 ments. >ince from this time forward radial fun-ows and tho-e that 

 are parallel t o t he eijuat .r make t heir a ppea ranee alternately, t he irerm- 

 disc is suldi\'ided into more and more numerous .segments, whic: 

 so arranged tliat the smaller lie at the centre of the disc, therefore 

 immediately around the animal pole.- tin- 1 irger toward it> periphery. 

 With the advancing cleavage the >m-iller >eLfiiuMits are entirely ODD 

 strictt.l ctl' from the undci lying yolk, whereas th. ; --ripheral 



one> .Ntill i emain at tir>t in continuity with it (tii:. .'H ). In thi> way 

 we tinally get a di>c ot small emhryonic ivll>. \\ hi-h. toward the 

 middle, are an a Hired in >i-veral >u[>er[o>ed la\ 



