CYTOLOGY OF HYDRACTINIA AND PENXAR1A. 223 



the male pro-nucleus is shown but its position, near or far from 

 the female pro-nucleus does not seem to influence the time when 

 the chromatin is to migrate from the nucleus. Immediately in 

 contact with each pro-nucleus, the cytoplasm becomes denser 

 and is composed of finer granules (cf. also Hargitt, Figs. 48, 49, 

 50). But isolated or wandering nuclear vesicles usually lack 

 this modification of the cytoplasm which has been used to assist 

 in recognizing the pro-nuclei. 



Figs. 12, PI. II., 15 and 18, PI. III., show some of the 

 chromatin granules close to the nuclear membrane as if they had 

 just emerged from the nucleus into the cytoplasm. In both 

 Figs. 15 and 18 these chromatin granules are on opposite sides 

 of the nucleus which indicates that their position is not the result 

 of the accident of cutting the sections. The male pro-nucleus in 

 Fig. 15 shows the same condition of the chromatin. After the 

 chromatin has been in the cytoplasm for some time, there are 

 found definite small vesicles usually empty. From the study of 

 mitosis in cleavage and the changes in the chromatin during the 

 anaphase and telophase, the suggestion that these vesicles are 

 the product of the transformed chromatin seems inevitable. 

 During this period, while the chromatin is migrating into the 

 cytoplasm, the chromatin both within and without the nucleus 

 takes a very faint stain so that the whole nucleus is easily over- 

 looked. Some of the most satisfactory results were obtained by 

 using Brazilian without the iron mordant. In no instance have 

 nuclei entirely devoid of chromatin been found. The vesicles in 

 Figs. 13, 14, 17, PI. II., and most of them in Fig. 12, are empty. 

 If the interpretation offered is correct, then there must be a very 

 large amount of chromatin that leaves the nucleus in Fig. 12. 

 The meaning of the large flask-shaped vesicle attached to the 

 female pro-nucleus in Fig. 15 is not understood. 



There is some question as to whether this process takes place 

 in all of the eggs preparatory to cleavage, but that it is very 

 common and appears in well fixed eggs there can be no question. 

 On the same slides were found mitotic figures preserved in all of 

 their parts. The slides showing many of these phenomena were 

 examined by Mr. George T. Hargitt who is at work on a similar 

 problem at Harvard University and he confirmed the correctness 



