276 J. E. S. MOORE. 
incident to the surrounding parts, than any alteration in the 
structure of the generative cells themselves. 
In fact, no definite change occurs in them till late in the 
second period, when ,the advent of the so-called “ reduction 
process” produces a sharp and definite alteration in the 
morphological value of all the elements affected. So character- 
istic is this change, that the time of its commencement can be 
used as a point of reckoning in all those reproductive cycles in 
which it is apparent. 
For the sake of clearness, that part of the reproductive cycle 
in Elasmobranchs which comes before the proper spermato- or 
ovo-genesis will be called the primary or embryonic period, 
while the cellular generations of spermato- or ovo-genesis before 
and after the numerical reduction of the chromosomes will be 
distinguished as those of the first and second spermato- 
or ovo-genetic series. 
It is my purpose in the present paper to give a detailed ex- 
position of the changes witnessed in the generative cells during 
the reproductive cycle of Elasmobranchs, after the completion 
of the embryonic period in the male, i.e. during the proper 
spermatogenesis in the fish, and then to draw such conclusions 
as may seem legitimate from a comparison with other forms. 
I. Technical. 
2. The materials with which the present investigation was 
carried out were obtained while I occupied the British Asso- 
ciation Table in the Naples Laboratory during the months 
of October, 1893,to July of the following year. They consist of a 
large number of Elasmobranch testes, including those of 
Scyllium canicula, Scyllium catulus, Pristiurus, 
Torpedo, Raja macrorhynchus, and Raja maculata, 
The testes were cut up into small pieces about the size of half 
a cubic centimetre, and fixed in various ways. I obtained the 
most successful preparations after the use of Flemming’s strong 
solution, Hermann’s fluid, osmic acid in various strengths, and 
corrosive sublimate, both with and without acetic acid. Valu- 
able comparative material was also obtained by treating the 
