STUDIES IN THE EXPEEIMENTAL ANALYSIS OF SEX, 597 
crabs were found in a state of nature to have recovered from 
the disease, the Sacculina having dropped off and left the 
characteristic circular scar on the abdomen where it was pre- 
viously attached. Of a large number of crabs experimentally 
freed of the parasite a few also survived for several months. 
Of these specimens, three which had recovered naturally and 
one which had been experimented on, were found to have re- 
generated the gonad, which had grown to a considerable size. 
The gonad was found to contain a certain amount of adult 
spermatozoa and a number of ova, some of them small and 
immature, others of a very large size and distended with the 
reddish-coloured yolk, which normally appears in the eggs as 
they approach maturity. 
The fact that the alteration of the male, under the influence 
of the parasite, is consummated by the final assumption of 
complete internal as well as external hermaphroditism is, I 
believe, without parallel, and confers on this case a peculiar 
definiteness and value which we cannot obtain elsewhere. 
The phenomenon appeared to me so strange and so little 
likely to gain credit from people who had not actually investi- 
gated the matter, that I was greatly pleased when Mr. F. A. 
Potts undertook, at my suggestion, to examine the matter in 
a parallel instance, namely the effect of the parasite Pelto- 
gaster on the hermit-crab, Eupagurus (15). The investi- 
gation of this case offered considerably more difficulty than 
the case I had examined, but he was able to obtain a series of 
results which happily place the main conclusions outlined 
above on a very sure footing. Stated concisely he found 
that, as in Inachus, so in Eupagurus the infected males 
assumed to varying degrees of perfection the female charac- 
teristics,^ but that the females, as in Inachus, never acquired 
any male characters, although they might show reduction of 
their own secondary sexual characters. The most remarkable 
result, however, obtained by him consists in the discovery 
that in a very large number of modified males, while the 
' The female characters assumed by the male are here, as in Inachus, 
those of the adult bi-eeding female. 
