(11) 



cleavage takes ^1^^^. I* it. rruri diorial ana at ri ,:ht aii^ieB to 

 the ^^■i^st, d.i vidian, the tv;o equal blastcmcrcs into four equal 

 blastoiricros. As Ikeda has obsorvca the ciuavat^^ dues not oc- 

 cur si.Tiultaneously in bo tn biastcmorcs nor aoes it in later 

 cleavagv-t*. {."^J-'S* ^) '^^'^ blastoKiere;:3 of th^c four-cell staf^e 

 whichi at -ft rst overlapped soon become applied to one another so 

 that the two meet in a cross fUrrow. C^ic.^) Shortly before 

 the third cleava^^e occurs the cross furrow disappears and the 

 blastomeres come to overlap, Tr.o third cleavafoC takes place 

 fifteen minutes after the secoiiu cleavage and it is equatorial. 

 The blastomeres become drav/n out into a more or less ovoid 

 shape and, as division takes place, the upper four olas tome ^^ij 

 become rotated in the dj. rection of tl:e hands of a v/atch, (■Pijj;.9) 

 The eigh^t blastomeres are approximately the same size as a rule, 

 and there is a siriall sedimentation cavity present which from now 

 on persists. CPi^.lO) The three polar bodies are aistint^uish- 

 able at this statue sometimes within the blastocoel ana sometimes 

 ^n the surface oV the blL.stomcres, The blastocoel is Oi^en at 

 the animal d,nd vegetal poles. The sixtccn-cell sta^e arises 

 from the eight-cell stat,;e by a meriaioi;al division of each of 

 its blastomeres but they ao not all divide simultaneously, 

 (■pig.ll) alti:ou(;h the difference in time is verj slight. 

 Ancr trio sixtcen-cell stare T could not follow t:;e individual 



