4g 

 comparatively early cleavages v/as tried a^d the parts were 

 four.d to cc'tirue their develorment ithout a;"y hindrance. 

 These experiirents v/ill')be described -ore in detail later. 



Another -noint in v;hich the segmenting egg of Turriton- 

 sis differs fro;r thrt of Oceania arMJif- is that it does not 

 for:", a triie cleavage cavity. The blastomeres r.lv/ays forn a 

 nore or less rolid enbryo, as shov.'n in "he sections of hese 

 stages. Occasionally there are sr:all spaces left between 

 the rells; but a true segmentation cavity that later ferns 

 a blactocccle is 'ever for-"ed. In this respect also it is 

 siTilar to the develOTtraent of Pennaria tiarella as describe, 

 by Hargitt. As the coT.nletion of segmentation anrroaches, 

 these irregular masres of cells gradually trke .n a -rove 

 sy"-r:etrical fori;! and finally there is formed an oval enbryo 

 co-^pcsed of e solid nass of cells constituting a rrorula. 



The first cleavage takes nlace about twenty to thirty 

 TTiinutes after the rclar bodies have been given of i . It 

 begins at the upner pole of the egg and passed down to ihe 



