CYTOPLASMIC INCLUSIONS OF THE GERM-CELLS. 
581 
present, but I am unable to advance any other opinion 
beyond this : I believe the cloud is formed by a growth and 
enlargement of the zone already indicated as being present in 
the cytoplasm of at least some germinal epithelial cells (PL 30, 
fig. 2, Y. and X.), which is quite possibly a conglomeration of 
some material around or in an attraction sphere. But so 
difficult is it to study these early stages that I cannot advance 
any evidence based on actual knowledge of this small aggre- 
gation in the cytoplasm. 
One significant fact I can, however, point out : it is that 
the growth or the appearance of this faint cloud is subsequent 
upon a change in the size and often of the staining power of 
the nucleus. The latter moves first ; the cloud then appears. 
In every case the germinal nucleus at first becomes round 
or oval, and the chromatin lumps, before connected here and 
there by bridges, become spherical and isolated. After this 
the cloud in the cytoplasm becomes marked. From this 
stage onwards there is a difference in the behaviour of the 
kinds of male cells derived from such progerminative cells. 
In the case of one generation of male cells, shown in Text- 
fig. 3, the chromatin lumps, after some slight changes, break 
into a spireme, and the prophases of the heterotypic division 
are undergone while the cell still adheres to the germinal 
epithelium ( C.F . in Text-fig. 3, i). The same sort of occur- 
rence invariably happens in the oocyte, where a spireme 
gradually appears and the prophases take place in situ. But 
in the case of certain cells shown in Text-fig. 2, ii, and 3, ii, 
the behaviour of the chromatin is different. It can at once 
be explained that this different behaviour is due to the fact 
that such cells are going to undergo mitosis. For this to 
happen the chromatin must come into a resting stage for the 
formation of a reticulum, which soon breaks up into chromo- 
somes. (See Text-fig. 2, ii, at 5.) 
In this last cell the chromosomes are beginning to appear. 
It has been customary for many writers on this subject to 
describe minutely changes in the nucleus which herald either 
the formation of a spermatogonium or an oogonium, whichever 
