CYTOLOGY OF HYDRACTIXIA AND PENNARIA. 23 I 



9. Maturation in Pennaria begins before the eggs leave the 

 medusa. The polar bodies are ephemeral in character and rarely 

 found attached to the deposited egg. The polar bodies are 

 formed by the mitotic process. 



10. After the two polar bodies are formed in Pennaria there is 

 a distinct migration of a considerable amount of chromatin into 

 the cytoplasm. The chromatin is transformed into vesicles which 

 eventually are taken up by the cytoplasm. Sometimes these 

 vesicles contain chromatin and persist for some time and may (?) 

 divide mitotically, giving rise to a pseudosegmentation. 



1 1. The spermatozoa may penetrate the egg before it is laid. 

 The sperm head is transformed into a male pro-nucleus which 

 moves through the cytoplasm toward the animal pole to unite 

 with the female pro-nucleus. 



1 2. Cleavage in Pennaria is at all times by the mitotic process. 

 The chromosomes become transformed into vesicles during the 

 late anaphase and early telophase. The vesicles may or may not 

 unite into a definite " resting nucleus " before the next cleavage. 



13. During cleavage in Pennaria there is a distinct centre- 

 sphere which contains granules with centrosome powers. This 

 centrosphere is more conspicuous in Pennaria than in Hydractinia. 

 The new prophase spindle arises within the old centrosphere. 



14. Papillae are found in both Hydractinia and Pennaria before 

 segmentation, much as described by Hargitt. 



15. A partial condition of fragmentation is seen in the migra- 

 tion of chromatin into the cytoplasm in both species. 



1 6. No clear evidence of amitosis was observed. 



17. Inclusions are frequently found in the egg of Pennaria. 



October 20, 1908. 



LITERATURE CITED. 

 Brauer, A. 



'91 Ueber die Entwicklung von Hydra. Zeitsch. f. w. Zool., Ed. LII. 

 Bigelow, H. B. 



'07 Studies on the Nuclear Cycle of Gonionemus Murbachii A. G. Mayer. Bull. 



Mus. Comp. Zool., Vol. XLVIII., No. 4. 

 Bunting, Martha. 



'94 The Origin of Sex Cells in Hydractinia and Podocoryne. Jour. Morph., 

 Vol. 9. 



