72 Proceedings of the Royal Physical Society. 
and bundles of thread-like spermatozoa as well as the characteristic bodies 
(Restkorper) from which the spermatozoa have escaped. The ‘‘groups” are 
often rosette-like in appearance, five cells in one focus and three in another 
being a common arrangement of the eight-nuclei stage. Sometimes, however, | 
the eight cells all lie in one plane (Pls. III. and IV. figs. 15, 22). The nuclei 
in a group are at about the same phase of development. 
With three or four exceptions where a large number of sections was cut 
only a few slides from one specimen were prepared for examination. 
The enormous number of gonad tubes, and their large size, combined 
with the smallness of the nuclear elements makes the inspection of one 
single section a somewhat lengthy process. 
There is a very marked difference in the appearance of the nuclei in 
the different specimens which at first might be attributed to the different 
effects of the various fixatives, but which was eventually proved to be due 
to the fact that the nuclei were at different stages of development (Flemming 
fixation, however, does make the nuclear elements larger, while at the 
same time it does not preserve the morula-like arrangement as firmly as 
do the other fixatives). Thus in all the sections cut from one given 
specimen the majority of the nuclei were in the resting condition—there 
being comparatively few prophases. In others again, by far the greater 
number were in the early prophase condition. In others yet again, telophases 
were most plentiful, while in quite a large number of the sections a sort of 
intermediate condition between late telophase and resting nucleus was charac- 
teristic. Whether all the different stages could be obtained from one individual 
specimen by sectioning the whole gonad has not been determined—the large 
‘size of the gonad precluding such a lengthy operation. 
This fact having been ascertained it became necessary to link up in 
sequence the different stages. By choosing unmistakable prophases or 
telophases and working backwards and forwards this was not a difficult 
matter—especially, as already stated, belated or precocious specimens 
could always be found interspersed among their more uniformally develop- 
ing neighbours. This abundant supply of nuclei at about the same stage of 
development, while entailing the preparation and study of a very large amount 
of material, is advantageous for securing the finer gradations of change. 
SPERMATOGONIAL DIVISIONS. 
The spermatogonial cells differ very much in size, the larger younger 
ones being nearest the walls of the gonad, the smaller older ones being 
nearest the central lumen. | : 
The resting nucleus (PI. III. fig. 1) isa more or less uniformly pale staining 
