HARGITT: PENNARIA TIARELLA AND TUBULARIA CROCEA. 207 
Addendum. 
Since this paper was written there has appeared a short paper by 
Cora Beckwith (:09) on the early history of the egg of Pennaria tiarella 
and Clava leptostyla. Beckwith finds that in both species polar cells 
are formed by a process of mitosis, which is in agreement with my 
results on Pennaria and ‘Tubularia. She finds, however, that this 
takes place between the hours of 4 and 6 in the morning, a condition 
not in agreement with my observations, since I found that eggs of 
Pennaria which were killed at 6 A. M., and later, possessed the germi- 
native vesicles; and only near the time of liberation of the medusa 
(about 7 Pp. M.) were maturation spindles and polar cells to be observed. 
This seems to show a considerable variation in the time of the comple- 
tion of the maturation process. 
Our results in regard to the fate of the nucleolus are also not in 
agreement, Beckwith finding that this body is cast into the cytoplasm, 
while I always found that it disappeared within the germinative 
vesicle before the dissolution of the nuclear membrane. Beckwith 
observed in Pennaria the fusion of the germ nuclei, and I, too, found 
this to occur, though apparently these nuclei may sometimes be sepa- 
rate, at the time of the formation of the first cleavage spindle. ‘The 
formation of chromosomal vesicles, which often persist, and the delay 
of the segmentation of the cytoplasm in the cleavage of Pennaria, are 
observations which I can confirm. 
