222 W. M. SMALLWOOD. 



three other eggs in the same phase of maturation. Pennaria was 

 collected by Professor Hargitt early in the morning and in the 

 afternoon but in the numerous sections made of the adult 

 medusae, none showed any earlier stages. With this data at hand, 

 however, it should be an easy matter to secure the intervening 

 stages which undoubtedly occur about the time the medusae are 

 set free. Sections of medusae still contained one or two eggs 

 which in each instance had completed maturation, Fig. 11, and 

 the polar bodies were not in contact with the egg. The condi- 

 tions shown in Figs. 47 and 49 by Hargitt are without question 

 polar bodies and probably the second. The state of the chroma- 

 tin vesicles in Fig. 47 is more regular than any that I have seen 

 which may be due to the preservation. They seem also to be 

 more scattered than any observed in eggs fixed in Bouin. The 

 clear area within the egg just beneath these vesicles was not seen 

 in the Bouin fixation. Another puzzling feature of this study on 

 maturation was the presence of small bodies attached to the sur- 

 face of the egg. They were especially noticeable on the eggs of 

 Hydractinia. After some study, it was apparent that they were 

 protozoa which in many instances looked exactly like polar cells 

 found in mollusca. 



CHROMATIN CHANGES IN Pennaria. 



The female pro-nucleus is a small, faintly staining body that is 

 found in eggs that are just laid and many that are still in the 

 medusa. Sometimes it was pointed at the outer end and pushed 

 close against the false membrane but it was never found protrud- 

 ing. It occupies this position until the approach of the male pro- 

 nucleus when it may move some distance from the periphery of 

 the egg. But before the fusion of the two pro-nuclei, there 

 occurs a series of unusual changes in the chromatin, especially of 

 the female pro-nucleus. Changes of a similar nature but not as 

 extensive are found taking place in the male pro-nucleus. The 

 chromatin changes described in Hydractinia preceded maturation. 

 These in Pennaria follow maturation. 



It is difficult to determine whether there is any order to these 

 changes and so no attempt is made to decide which is the older 

 state in the series of Figs. 12 to 1 8. In several of these figures 



