GYTOPLASMIC INCLUSIONS OF THE GERM -CELLS. 565 
the yolk cells (N.G.) and the layer of Ancel (A.L.N.). 
According to the sort of sex cells in any given region the 
germinal epithelium is characteristic. Where rapid pro- 
liferation is taking place, where yolk cells are abundant, or 
where a large oocyte is present, the epithelium lias a special 
appearance. In PI. 30, figs. 3 and 7, and in PI. 31, figs. 9, 11,. 
and 12, where an oocyte is in growth, the germinal epithelial 
cells tend to either become atrophied or altogether pushed 
aside. In Text-figs. 1, 2, 3, and 4 are drawn typical portions 
of the ovotestis under different conditions. It will be seen 
that the appearance of an alveolus of the ovotestis may vary 
greatly. Not only does the wall differ at different stages, but 
the contents of the lumen are rarely the same in appearance. 
I believe that the varying different stages in the alveoli 
can be classified for different seasons of the year, though 
if the ovotestis is sectioned during hibernation it will 
be found that all the various sorts of alveoli are present. 1 
Then one is led to inquire what causes individual alveoli of 
the ovotestis to vary so remarkably in appearance as do those 
drawn in Text-figs. 2 and 3. Ancel has given a description 
of the metamorphosis of the alveolus in the young snail, 
which, in view of his Flemming technique, is not very satis- 
factory. Unfortunately his methods did not allow him to do 
anything but describe the nuclei, but from his otherwise admir- 
able description we know that the following events take place : 
Firstly the male progerminative cells appear and drop into 
the lumen. Then the germinal epithelium becomes arranged 
in two layers, the inner of which remains indifferent, the 
outer (next to the male cells) becoming converted into nurse- 
cells. Thirdly, the inner layer of an indifferent nature 
sporadically gives rise to oocytes. That this is reallv what 
happens I have no doubt, and if one keeps this description 
of the sequence of events in one’s memory, some difficult 
problems with which one meets in studying the adult ovo- 
testis become less hard to understand. 
1 But the orders of cells differ in the seasons. This matter is dealt 
with in a forthcoming paper. 
