"2 Art. ?. - Naohide Yatau : 



far from the shore. The water taken near the city of Naples was so 

 polluted that it was unfit for use in developing egg-fragments into 

 embryos. This is the indispensable condition for ctenophore 

 experiments. The high mortality in Driesgh and Morgan's work 

 seems to have been due to tlie neglect of this precaution ('95 p. 

 217). To obtain eggs two or three animals were kept in a rather 

 small cylindrical jar, so that they stirred the water more or less 

 when swimming and kept the eggs they laid constantly in motion. 

 If, on the contray, the ctenophores be put in a large jar, the eggs 

 are liable to stay near the surface ; there they l)ecome weak and 

 give rise to less lively larvae or fail to develop at all. 



I. Structure of the Egg. 



The eggs of the following four common species of ctenophores 

 were studied; namely Beroë ovatu, B.fonkalii, Callianira hialata and 

 Eucharis vmUicornis. The relative sizes of the eggs of these forms 



are shown in Fig. I {cf. Chun 

 '80 p. 100). The egg of 

 Beroë ovala was the one most 

 carefully studied and exclu- 

 sively used in experiments, 

 being peculiarly suited for 

 the purpose on account of its 

 large size (1-1.2 mm) and 

 of its consistency. 



When the eggs are laid, 

 they are found entangled in 

 a string-like mass of jelly. 

 Close to the egg is a thin 

 gelatinous covering that 

 turns into a thick layer of 

 jelly after fertilization.^ The 

 egg has three visible con- 



PlG. I. 



Diagram showing the relative sizes of ihe eggs of 

 Callianira hialata (1), Eucharis viiilticoriu's (2), 

 Beroë forskalii ^3) and B.ovata (4). X6> 



1 The eggs of Eucharis multiconiis can be more easily taken out of the jelly than those of 

 Beroë, 



