184 CORA JIPSON BECKWITH. 



maturation and fertilization processes were supposed to take 

 place while the chromatin is in this unstaining condition, the 

 sperm having also lost its staining capacity after entering the 

 egg. The first evidence of nuclei in the egg after the disappear- 

 ance of the germinal vesicle was found in the appearance of 

 ' nuclear nests " or groups of small vesicles scattered throughout 

 the egg, several such nests usually occurring in an unsegmented 

 egg. In Pennaria not less than four such nests appear simultane- 

 ously indicating four centers of nuclear reconstruction. In 

 Clava, as I understand the description, this condition of several 

 nuclear groups occurs occasionally in an unsegmented egg. More 







often, however, eggs were found already segmented with a single 

 resting nucleus in each cell which I take it were believed to arise 

 as described for Pennaria. This reappearance Hargitt thinks is 

 explicable on the ground that after fertilization the chemical or 

 physical conditions again change so that the chromatin once more 

 responds to stains. The chromatic material that was scattered 

 at the time the nucleus disappeared collects again, forms vesicles 

 which especially in Pennaria occur in groups or nests, each nest 

 finally fusing into a single nucleus. Thus a syncytium arises 

 without mitosis and with no apparent evidence of maturation or 

 fertilization having taken place in the egg. In Pennaria after 

 these nuclear groups are formed, nuclear proliferation is by 

 mitosis. In Clava leptostyla, however, up to the sixteen-cell 

 stage Hargitt describes nuclear proliferation by amitosis, later 

 cleavages being mitotic. 



The points in question accordingly are: (i) The nature of 

 maturation and fertilization processes, (2) the formation of 

 nuclei de novo, and (3) the role of amitosis and mitosis in early 

 cleavages. 



Pennaria and Clara Icptostyla were preserved at Woods Hole 

 where Hargitt obtained his material. Also the same killing fluids 

 and stains were used so that the question of method is eliminated. 

 Material was killed every hour of the day and night and every 

 half hour in the early morning hours which proved to be the 

 most important period. 



I found in both Pennaria and Clava leptostyla that in material 

 killed between the hours of 4 and 6 A. M., it was possible to 



