578 
J. BRONTE GATENBY. 
shape — probably traceable to the cramped quarters in which 
the cell is forced to metamorphose. 
In Text-fig. 1, iii, iv, the two extremes in these various 
kinds of cells are drawn. Fig. iii shows the typical Neben- 
keru formed of many curved rods, while fig. iv shows the 
typical rectangular Nebenkern formed of fewer elements. 
The remarkable differences which are found in the later 
spermatids are illustrated in PI. 33, figs. 37 and 40. These 
are not quite at the same stage, the latter being slightly 
younger. In this form the Nebenkern is very large and 
peculiar, differing most markedly from that in PL 33, fig. 37. 
This also applies to the mitochondria, which, while being 
larger in PI. 33, fig. 40, and fewer. But, as will be noticed in 
PI. 32, fig. 26, largeness of mitochondria and smallness of 
Nebenkern batonettes do not necessarily go hand in hand. 
The Manner of Metamorphosis of an Indifferent 
Germinal Epithelial Cell into a Primary Sper- 
matogonium . 
Many of the older writers thought that the main factor of 
change in the epithelial nucleus was the appearance, or at 
least the exaggeration, of the chromatin lumps. PL 31, 
figs. 11 and 19 show this. In one case we deal with a sperma- 
togonium (the latter), and in the other with a oogonium. But 
it should at once be pointed out that, from a careful study 
of these stages, I have concluded that the amount of real 
Fig. i. — Part of the lumen less well supplied with nutriment. The 
epithelial cells have here and there grown into progerminative cells 
(X), passed to the prophases of the heterotypic division ( C.F .) and 
afterwards have begun to drop off (X.Y.). (Text-fig. 4.) At X. and 
E.N.C. are yolk cells in stages of disintegration. At N.C.N. is a 
bare yolk cell nucleus. At S.N. are many sperm atogonial nuclei 
lying in a syncytium (R.), a quite characteristic occurrence in these 
localities of a lumen. As at S. and in other cells there is a 
distinct cloud near the nucleus. (See PL 31, figs. 19, 20 ; Pl. 32, 
figs. 21 and 23.) Fig. ii. — Passage of a male progerminative cell 
(primary spermatogonium) from its place on the germinal epithelium 
