32 ART. 17. — N. YATSU. 



are thick walled strongly suggesting the 4 V-larvœ of the 8-cell 

 stage (Fig. 2G H, I; cf. Fig. 20 G-J). Often fusion takes place 

 between two or three eggs, when kept long in Ca-free sea-water 

 and in ordinary sea-water such conglomerates turn into gigantic 

 pilidia of grotesque appearance as is shown in Fig. 2G L. 



The above fact clearly shows that Ca-free sea-water peculiar- 

 ly inhibits differentiation and consequently embryogeny, whereas 

 it does not at all prevent cell-multiplication. And moreover it is 

 to be noticed that Ca-free water does not completely annihilate 

 the power of tissue differentiation, since embryogeny is resumed 

 in ordinary sea-^vater. 



III. Summary. 



The results of the foregoing experiments upon the egg of 

 Gerehratulus lacteus may be summarized as follows : 



1. The germinal localization does not progress for the space 

 of at least five hours after release, if kept unfertilized. 



2. The germinal localization becomes more definite on the 

 entrance of the spermatozoon. 



3. If a portion of 07ie of the blastomeres is cut off during 

 or after the completion of the first cleavage, no matter what 

 plane the section may strike, the resulting deformity is very 

 slight. 



4. If horizontal cuts in the animal region or oblique sections 

 in any region made on both the blastomeres during or after the 

 completion of the first cleavage, the effect is not great. 



5. If horizontal cuts be made along the equator or above it 

 anenteria often result. 



