Helen Dean King 351 
THE SECONDARY SPERMATOGONIA. 
The secondary spermatogonia are much smaller than the parent cells, 
and, owing to compression, they are more or less polygonal in outline. 
The earlier generations of these cells have a conical shaped body with the 
apex of the cone turned towards the centre of the cyst in which they are 
contained. As the cells increase in number they are closely crowded to- 
gether and the cell outlines become constantly more angular and irregular 
(Figs. 6-9). In the earler generations of these cells the nucleus is 
polymorphic in form (Fig. 6), but in the later generations it is usually 
round or oval. In the resting cell the chromatin is again distributed on 
a linin meshwork in the form of small granules. These granules stain 
somewhat more deeply than during the earlier period and their distribu- 
tion is not so regular (Fig. 6), as in many places groups of them become 
massed together so that the nuclear reticulum appears jagged and uneven. 
There are rarely more than five nucleoli in the nucleus of a secondary 
spermatogonium; of these one or two are plasmosomes, the others 
karyosomes. 
I have never found the secondary spermatogonia dividing amitotically 
as they do occasionally in Salamandra according to Meves. The pro- 
phases of mitosis in these cells are essentially like those in the primary 
spermatogonia. All of the nucleoli disappear and the chromatin forms 
into a thick, apparently continuous spireme which breaks into twenty~ 
four segments of different lengths (Fig. 7). The chromatin segments 
soon condense into V-shaped chromosomes which are somewhat smaller 
than those found in the primary spermatogonia. 
The spindle in the secondary spermatogonia (Figs. 8, 9) is shorter 
and somewhat broader than that found in the parent cells (Fig. 5). It 
also has no radiation around the centrosomes at the spindle poles. The 
centrosome, attraction-sphere and the acroblast appear in the resting 
stages of the secondary spermatogonia as they do in the primary 
spermatogonia. 
THE SPERMATOCYTES. 
The last division of the secondary spermatogonia gives rise to a new 
generation of cells, the primary spermatocytes, in which occurs the in- 
teresting, yet perplexing, series of changes that brings about a reduction 
in the number of the chromosomes preparatory 1o the maturation mitoses. 
The resting nucleus of the young spermatocyte usually occupies an 
eccentric position in the cell. It is invariably round or oval with a 
smooth contour (Figs. 10, 11) and never has the irregular outline com- 
