CYTOPLASMIC INCLUSIONS OF THE GERM-CELLS. 571 
the year except the hibernatory ones. 1 I have found that 
properly to describe the remarkable facts concerning the 
origin, function, and fate of the nurse or yolk cells alone would 
need a separate paper, and should circumstances allow I hope 
to apply myself to this task. 2 Bolls Lee (9) was struck by the 
number and varying sizes of the spermatogonia in the snail. 
I can at present think of at least several sorts of spermato- 
gonia ; by this I mean that it is quite possible to find a large 
number of cells which are in the spermatogonial generation 
of the male cells, and which differ markedly either in their 
nucleus, their Nebenkern, or their mitochondria. 
Cell Generations in the Snail. 
The most important result of this study has been the 
realisation that in observing the mixed mass of cells in the 
lumen of the ovotestis, one deals not with one generation of 
male cells derived in the same way, but with several genera- 
tions whose origins are in certain ways considerably different. 
It is not intended at this juncture to attempt any explanation 
of this until the various cells have been described as well as 
possible. From the excellent work of Bolls Lee (9) and 
Ancel (2), not to mention some of the older writers, we are 
fairly well acquainted with the appearance of the typical 
lumen of the ovotestis. Inspection of the text-figures will serve 
to show what these authors have failed to emphasise suffi- 
ciently, viz. that the appearance of the various alveoli differs 
greatly, not only individually, but just as importantly in the 
contents of the alveoli which are different at different levels. 
In Pl. 32, figs. 28 and 29, and PI. 33, figs. 30, 31, 32, 33, 
34, 35, 36, and 37 I have drawn typical stages of the meta- 
morphosis of a sperm from the loose cells lying in the open 
lower region of the alveolus. 
The spermatogonial division is drawn in PI. 32, fig. 28. 
Typically one gets small mitochondria often so small as to 
1 This has now been done. 
2 This paper (Part iv) lias lately been finished. 
