346 
HERBERT H. BROWN. 
darkly with hsematoxylin and present the ordinary appearance 
of resting nuclei ; they contain an irregular coarse chromatic 
network embedded in a stroma which stains less darkly, and 
are bounded by a nuclear membrane (fig. 1, b). These I shall 
call growing cells. 
(3) The other cells in the outer layer, which might easily 
be overlooked, are much fewer in number than those last- 
mentioned, and their nuclei are larger, somewhat paler, and 
more homogeneous in appearance, the chromatic substance 
being diffused in a very fine network throughout the nucleus 
(fig. 1, a). These appear to me to be the cells from which all 
the other elements of the tubule, with the exception of the 
supporting cells, are derived, and I shall therefore call them 
spore-cells. Probably they are the direct descendants of the 
primitive male ova. 
The cells of the second layer are large, and contain large 
spherical nuclei, which are all in the kinetic condition. At 
this stage the nuclei form for the most part a single row, but 
here and there a cell is seen containing two nuclei, one being 
internal to the other. These correspond to the growing cells 
of the outer layer of the preceding generation, which have 
now attained a considerable size. They are destined to divide 
by karyokinesis into groups of cells which ultimately become 
spermatozoa. They are in fact growing cells which have nearly 
finished growing. 
The third layer (fig. 1, c) is composed of smaller cells, three 
or four deep, with spherical nuclei which are pale, containing 
only a small amount of chromatin. These cells have been 
called spermatoblasts, spermatocytes, &c., but since each cell 
is destined to develop into a spermatazoon, I shall call them 
simply young spermatozoa, or young spermatozoa 
with spherical nuclei. 
The fourth layer is composed of spermatozoa which are just 
ready to leave the tubule. Between the heads of the sperma- 
tozoa and the cells of the third layer, there are numerous 
irregular darkly-stained granules 1 (fig. 1, x), each granule 
1 These bodies are the “ seminal granules ” which have been so often 
