STUDIES IN THE EXPERIMENTAL ANALYSIS OE SEX. 261 
and only very occasionally a moderately intense yellow colora- 
tion. It is very tempting to correlate this feeble formation of 
lipochrome in the blood of injected Carcinus with the very 
slight modification which the infected individuals undergo in 
their primary and secondary sexual characters in general, in 
comparison with Inachus. As Potts has shown, and I have 
repeatedly confirmed, the only effect of the parasite on Car- 
cinus is to cause the abdomen of the male to become slightly 
broader in a certain percentage of cases ; we never obtain the 
development of female appendages by the male or the full 
assumption of the female shape of the abdomen, such as 
frequently occurs in Inachus. The effect on the internal 
generative glands is also not nearly so Avell marked. The 
difference that Robson and I have found in the blood of the 
two infected forms, therefore, corresponds very well with the 
other features of the modification induced by the parasite in 
the two cases. 
In the case of the effect of the parasite on the liver, how- 
ever, our results agree completely. In both Inachus and 
Carcinus the infected crabs of both sexes almost invariably 
possess an opaque white or yellow liver in which a very large 
quantity of fat can be detected either by micro-chemical 
means or else by extraction methods. I have found in 
Carcinus that the liver of infected crabs is not only 
constantly full of fat but also deeply stained with yellow 
lipochrome, and this is the case at all times of year and in 
every phase of the infected animal’s life, while the normal 
individuals exhibit great variations at different periods in the 
fat content of their livers. This, in itself, is an observation 
of first-rate importance in the theoretical interpretation of 
the effect of Sacculina on its host, since it proves beyond 
cavil that at any rate Sacculina does influence the fat 
metabolism of its host in a very positive degree. It is 
interesting to note also that in the effect on the liver 
Carcinus and I nacli us react in the same way to the presence 
of the parasite ; and this may be termed the first reaction to 
the parasite. The second reaction, namely the flooding of the 
