356 
HERBERT H. BROWN. 
measure mechanical; they serve the purpose of supporting and 
keeping in order the complex testicular epithelium, forming a 
sort of sustentacular framework like that of the Mullerian 
fibres of the retiua. They serve for the support of, and also 
probably convey nutritive material to the young spermatozoa 
during their development, and when this is completed they 
expel them into the lumen of the tubule. 
I must now return to the history of the development of the 
spermatozoa, at the point at which I left off to describe the 
supporting cells. We have at present reached the stage of 
fig. 2 in the fourth cycle. 
A young spermatozoon at this stage is somewhat conical in 
shape, the rounded apex of the cell, which is directed outwards, 
being occupied by the nucleus. 
The nucleus has become oval and projects from the cell 
protoplasm so that its outer hemisphere is covered only by the 
clear cap. As the development progresses the nucleus lengthens 
out, and projects more and more from the cell, until finally 
only its inner extremity remains embedded in the protoplasm. 
The projecting part of the nucleus is covered by the clear cap 
which increases with it, but when the hooklike form of the 
nucleus is established (fig. 6, d) the clear cap is no longer to 
be seen. 
As the nucleus increases in length it diminishes in thickness, 
and becomes more and more intensely stained by hsematoxyliu ; 
there is no chromatic network, but the chromatin appears to 
be uniformly diffused throughout its substance. Before long 
the nucleus begins to curve (fig. 4) and the hooklike shape of 
the head of the spermatozoon is established by the time the 
stage of fig. 6 is reached. 
The remainder of the process is occupied chiefly by the 
development of the body and tail of the spermatozoon, and 
can be studied much more satisfactorily from teased osmic acid 
preparations, from which the series of drawings (figs. 16 — 24) 
is taken. Growing spermatozoa at an early stage corresponding 
to fig. 14 are represented by fig. 22, a. They are small cells, 
elongated in a radial direction and contain a spherical nucleus 
