384 KING. [Vort. XIX, 
cording to Eismond (27) an ovum may arise either from one 
of the cells of a nest which has outstripped the others in 
development, or from a fusion of all of the cells of a cyst. He 
also considers that “‘la formation des nids n’était pas un anneau 
indispensable dans le cycle de l’oogenése, c’est-a-dire qu’en 
méme temps que la formation des nids du sens strict, se faisait 
aussi la différenciation progressive des oocytes directement 
aux dépens des produits de la derniere division des odgonies, 
comme cellules independantes.”’ The conclusion that ova may 
arise directly from oogonia accords with the view advanced in 
1870 by Waldeyer (91) and supported later by the researches 
of Balfour (4) on elasmobranchs. 
Bouin has investigated the formation of the ova in much 
greater detail than have any of the other workers on amphibian 
oogenesis. He finds, as do other investigators, that secondary 
oogonia are enclosed in cysts, and he states that all of the 
oogonia in a cyst divide simultaneously. After several 
divisions, the number of which he does not determine, the 
character of the cells changes considerably and “oogonia of 
transition” are formed. ‘The latter are clearly defined cells 
with rounded nuclei in which there are several chromatin 
nucleoli, but no traces of a chromatin reticulum. This stage 
is succeeded by one in which the nuclear membrane disap- 
pears and the karyoplasm is separated from the cytoplasm 
only by clear area. At a later stage of development granular 
threads appear in the nucleus which are formed, doubtless, of 
the minute chromatin granules scattered in the karyoplasm. 
These threads increase in number very rapidly and form a 
distinct chromatin reticulum, while a new nuclear membrane 
encloses the nuclear contents. All the cells of a cyst develop 
up to this stage, but later, owing to some unknown causes, 
only a part of the cells continue their development as oocytes ; 
the others degenerate and are either dissolved gradually or 
devoured by the phagocytes. Degenerating cells never form 
follicle cells but probably serve as nutriment for the victori- 
ous oocytes. The results of Bouin’s investigations agree es- 
sentially with those reached by Balfour in his study of 
