STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 449 
intrusive nature. At the tops, and round the edges in places, 
are tubules lined with living and actively proliferating 
spermatogonia (PL 45, fig. L9). 
No. 11. — Male frog, in which both testes were severed 
from all connections and left in the peritoneal cavity 
October 4th, 1909. Killed March 30th, 1910. Time in body, 
6 months. Both testes were found attached to peritoneum 
with very slight vascular supply. One testis (fig. 20) was 
much reduced in size, and surrounded by a thick fibrous layer 
containing a large amount of pigment. The inner part 
consists of fibrous tissue, while round the edge are tubules 
containing living spermatogonia (fig. 21). There are no 
traces of spermatozoa. 
In the other testis (fig. 22), which is much larger, one end 
corresponds to the structure of the first testis, being com- 
posed of tubules with living spermatogonia and no sperma- 
tozoa, but with a considerable intrusion of fibrous tissue. At 
the other end are tubules with some spermatogonia and 
bunches of spermatozoa in the first stages of disintegration. 
In the centre of the testis are tubules with more completely 
degenerate spermatozoa and a certain amount of fibrous 
tissue. The vascularisation and connection of the testis with 
the body is at the upper end, where the spermatozoa have 
disappeared, and there is a large amount of fibrous tissue. 
Results of Transplantation Experiments given above. 
In all cases of allo-transplantation where the testes are 
transferred from the body of a male to the peritoneal cavity 
of another individual, whether male or female, the same 
processes of degeneration, absorption and replacement by 
fibrous tissue take place. In ten or eleven months the 
original testicular tissue has practically disappeared and 
nothing remains but a very small nodule of fibrous scar- 
tissue. In all cases the testis placed loose in the peritoneal 
cavity becomes reattached and vascularised. Within a 
month the ripe spermatozoa present in the tubules begin to 
