446 
GEOFFREY SMITH AND EDGAR SCHUSTER. 
the side by which attachment to the body of the host was 
effected. This fibrous tissue is continuous with strands of 
similar tissue ramifying between the testis tubules. It seems 
certain that the broad outer band of fibrous tissue is derived 
from the host, but the origin of the inner strands is doubtful, 
as they may be derived by a growth of the connective tissue 
which is normally present between the tubules. 
The spermatogonia or germinal cells lining the tubules 
have completely disappeared. 
No. 4. — Female frog, ovaries removed, and two testes from a 
male implanted October 8th, 1909. Killed April 7th, 1910. Time 
in body, six months. The two testes found attached to peri- 
toneum with blood supply. The one testis is much larger 
(fig. 4) than the other (fig. 5). In both the clumps of sperma- 
tozoa are degenerate (fig. 6), and there is a great invasion of 
fibrous tissue, especially in the smaller testis. In the latter 
( fi g- 7 ) the fibrous tissue has invaded the tubules, and 
granules of chromatin derived from broken-down spermatozoa 
are found lying in the fibrous network. 
The spermatogonia have completely disappeared. 
No. 5. — Female frog, ovaries removed, two testes from a 
male implanted October 10th, 1909. Died May 5th, 1910. 
Time in body, 7J months. Testes attached with vascularisation, 
one to peritoneum of body-wall, the other to the remains of 
the ovary. The microscopic appearance of these testes is 
very similar to those of No. 4. The invasion of fibrous tissue 
to replace the tubules and the degenerated spermatozoa has 
proceeded very far, and again is more advanced in one testis 
than in the other. Again, there are no traces of spermatogonia 
lining the tubules ; they have entirely disappeared. The 
testes are much reduced in size. 
No. 6. — Female frog, with one testis from male frog C, 
implanted September 30th, 1910, died August 11th, 1911. 
Time in body, 104 months. Testis (fig. 8) has shrunk to a 
very small size, about one eighth of its original dimensions. 
It was attached to the body-'wall, near the anterior abdominal 
vein. The microscopic structure shows that the greatly 
