STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 447 
reduced testis now consists almost entirely of fibrous tissue, 
among which the scanty remains of the granules derived from 
the broken-up spermatozoa can be recognised in places 
(fig. 9). Beyond these scattered granules absolutely no 
remains of germinal tissue are left, the whole having been 
replaced by fibrous scar tissue. 
Allo-Transplantation op Testes into Male. 
Three successful experiments were performed of this kind, 
and the results agree completely with the foregoing, showing 
that the destruction of the adult spermatozoa and of the 
spermatogonia and their replacement by fibrous tissue, prob- 
ably derived from the host, occurs equally when the testes 
are transferred to another male as when they are trans- 
ferred to a female. Thus — 
No. 7. — Male frog, with one testis from male B, implanted 
on September 29th, 1910. Killed on November 6th, 1910. 
Time in body 1£ months. This experiment is exactly parallel 
to No. 1, in which the other testis from male B was placed 
into a female for the same period. The result in this case 
was quite similar. The testis was found reattached and vas- 
cularised (fig. 10). The spermatozoa, especially in the interior of 
the tubes, have undergone considerable degeneration, though 
some of the bundles are still intact (fig. 11). The sperma- 
togonia have begun to disappear, leaving vacuoles round the 
edges of the tubules, but the germinal nuclei can still be 
recognised as present in small numbers. 
No. 8. — Male frog, with one testis from male A, implanted 
on September 29th, 1910. Killed December 15th, 1910. 
Time in body 2 b months. This is a parallel experiment to 
No. 2, and shows (fig. 12) about the same amount of 
degeneration and a considerable increase of fibrous tissue 
(cf. fig. 1). Phagocytosis of degenerate spermatozoa is 
proceeding. The spermatogonia have almost entirely dis- 
appeared, this degeneration having proceeded further than in 
No. 2. 
