GERMINAL LOCALIZATION IN THE EGG OF CEREBRATULUS. 11 



gut or tlie apical organ. The part above the plane b is able 

 to give rise to a pilidium with a defective gut but without the 

 apical organ (Fig. 6. a, A). The cut along c affects the pilidium 

 only in slightly malforming the gut and the ciliated lappets 

 (Fig. 6. b, B). The cuts below c, e. g., d, e, f do not interfere 

 with the niorphogenic processes at all, although a slight defect 

 is sometimes produced in the ciliated lobes. 



Nine arrhenokaryotic larvie were obtained. The study of 

 them leads to the following conclusion. The portion below the 

 plane f (Fig. o B) gives rise to a solid cell-mass. In the frag- 

 ment beloAv the plane e an invagination takes place, but no 

 apical organ is formed (Fig. 6 d, D). The part below d may 

 produce a perfect larva (Fig. 6 e, E), but often the apical organ 

 is not normal (Wilson '03, p. 443., Fig. 10 B). The cuts along 

 c, b and a cause hardly any deformities at all. 



This series of experiments clearly shows that firstly the 

 entodermic basis is present also near the animal pole and 

 secondly the apical organ basis extends into the vegetal hemi- 

 sphere. 



Series E. Removal Experiment during the First Cleavage, the 

 Cytoplasm being cut off from One Side of the Egg. 



When the first cleavage was going 



on, a portion of cytoplasm was cut 



off along various planes, such as a, 



b, c of the accompanying diagram 



j.^^. y (Fig. 7). Thirteen pilidia were ob- 



Diagram showiDg cutting Gained and the results may be tabu- 



planes in Series E. lated as follows : 



