THE DEVELOPMENT OF THE SPERMATOZOA. 429 
on cells and nuclei, in which he gives an account of the 
formation of the spermatozoa in salamander. ‘The interest- 
ing point for our purposes is that which refers to the forma- 
tion of the head of the spermatozoon, not, as has been sup- 
posed since the observations subsequent to Koiliker’s paper 
appeared, from the whole nucleus, but from that part of it 
which he calls the “ chromatin.” This collects into a spirally 
folded mass, which becomes more closely folded as it in- 
creases in length, till the whole head may be seen coiled up 
in the nucleus. The origin of the tail he traces to the cell 
plasma. These observations agree with those of Kolliker if 
we substitute spermatozoon head for the whole sperma- 
tozoon. 
I have not worked with sufficient detail to determine the 
exact origin of the spermatozoon head, but I must confess 
that my ideas agreed with those of previous observers that 
the whole nucleus took part in the formation of this struc- 
ture, though, since the publication of Flemming’s paper, I 
should not like to say that it was so, and can only hope to 
make some observations on its exact origin in the Mammalia. 
In the earth-worm it is not possible to distinguish in the 
nucleus ‘‘ chromatin” from other constituents, and hence 
the head of the spermatozoon cannot be traced in this case 
to such an element. 
The most recent utterance on this subject is by Meyer, 
in the ‘ Memoirs of the St. Petersburg Academy,’ tome xxxii, 
1880, and as it contains many figures confirmatory of my 
views, I purpose to give a slightly more lengthy account 
of it. 
His observations were made on the dog, cat, rat, mouse, 
bear, rabbit, and guinea pig. In a testicular tubule next 
the wall are found the Ursamenzellen, which consist of two 
kinds of cells, one small, often darkly granular, which he 
calls follicle cells, the other larger, with large nucleus, each 
containing a nucleolus, the nucleus itself being surrounded 
by a clear plasma. 
These would be the outer seminal cells of Klein, or what 
I have called the testicular epithelium and its interstitial 
cells. 
The first change which an Ursamenzelle undergoes is 
division. This takes place in a tangential direction, and 
the cell which is directed towards the lumen of the tube 
takes on the characters of a spermatocyte, which consists in 
the nucleus and plasma becoming darker and more granular 
(cf. his Taf. ii, fig. 94). The spermatocytes thus formed by 
division from the Ursamenzellen gradually increase in size 
