NOTES OX COKLOPT.ANA BOCKI n. sp. 



579 



Fig. 1 Flg. 2 



Fig. I. Newly laid egg. x 170. Fig. 2. A stage during gastrulation, 

 ec. Ectoplasm. seen from the micromere pole. 



en. Endoplasm. x 170. 



m. Egg membrane. mac. Macromeres. 



/. Polar bodies. mie. Micromeres. 



Development. — The segmentation of egg goes on in practically the 

 same way as known from ordinary ctenophores. As in these, the third 

 cleavage furrows are oblique and the resulting eight cells are arranged 

 in the " disymmetrical " manner. The succeeding divisions, which lead 

 to the formation of micromeres, are accomplished in nearly the same 

 manner as was described by Ziegler :) for Beroc and by Yatsu 2) for 

 Beroe' and Callianira. 



The gastrulation occurs in precisely the same way as in ordinary 

 ctenophores. At the close of segmentation there is a stage in which 

 sixteen macromeres are arranged in a bowl-like group covered on the 

 concave side (micromere pole) by an assemblage of numerous micro- 

 meres. Then, some " mesodermal cells are budded off from the 

 macromeres on the convex side of the group (macromere pole), while 



1) Ziegler, H. E., 1898. Experimentelle Studien über die Zelltheilung. III. Die Fur- 

 chungszellen von Bero'è ovata. Arch. Entwicklungsmech. Bd. 7, p. 34. 



2) Yatsu, N., 191 1. Observations and experiments on the ctenophore egg: II. Notes 

 on early cleavage stages and experiments on cleavage. Annot. Zool. Jap., Vol. 7, p. 333. 



