362 
HERBERT H. BROWN. 
Review of the Literature of Mammalian Sperma- 
togenesis. 
I will uow give a brief account of some of the different 
views upon mammalian spermatogenesis which have been put 
forward during the last fifteen years, describing chiefly those 
which are of most interest for the purpose of comparison. 
For this I am to a considerable extent indebted to the 
digest of the literature upon the subject which is given by 
Renson in the ‘Archives de Biologie^ for 1882, in his paper 
upon “ Mammalian Spermatogenesis.” 
Yon Ebner, in 1871, gave an account of spermatogenesis, 
taken from a study of the testis of the Rat by means of sec- 
tions, which has received a good deal of support. 
The supporting cells are described under the name of sperma- 
toblasts, and are considered to be the parent cells of the 
spermatozoa, which are formed endogenously from the proto- 
plasm of the spermatoblasts. Von Ebner describes an external 
layer, resting upon the wall of the tubule, composed of two 
kinds of cells, which differ from one another in the appearance 
of their nuclei, some of them having large nuclei which con- 
tain a spherical nucleolus, and others containing small granular 
nuclei. The cells with the large nuclei are the “ spermato- 
blasts.” The protoplasm of each spermatoblast joins that of 
its neighbour on each side, to form a sort of protoplasmic 
network upon the wall of the tubule, in the interstices of which 
are contained the small cells with granular nuclei. On the 
inner side the spermatoblast gives off a protoplasmic process, 
which extends radially towards the lumen of the tubule. The 
inner extremity of this process enlarges and splits up into 
digitations, and at the base of each digitation a nucleus de- 
velops, being formed out of the protoplasm of the mother cell ; 
then the nucleus elongates and becomes the head of a sperma- 
tozoon, a filament grows out from the extremity of each digi- 
tation and forms the tail, while the protoplasmic digitatiou 
itself is converted into the middle piece. During their de- 
