252 
GEOFFREY SMITH. 
At the time when these observations were put forward, I 
did not suspect that a means was ready to hand for testing 
this hypothesis, and that the French observer Heim (1) 
several years ago had observed that the blood of many 
female crabs at the time of the ripening of the ovary becomes 
charged with a brilliantly coloured yellow or orange lipo- 
chrome, which, according to Heim, is entirely absent from 
the male. Since lipochrome is invariably associated with 
fatty substances, in which it is soluble, it was at once 
apparent that Heim’s observation had a very direct bearing 
upon our problem; at my suggestion, therefore, Mr. G. C. 
Robson undertook to investigate the question in Inachus at 
Naples, while parallel observations have been made by 
myself on Carcinus msenas at Plymouth. 
As far as the course of events in normal uninfected crabs 
is concerned, Robson’s observations on Inachus and my own 
on Carcinus agree in every particular, but in the crabs 
infected with Sacculina the two sets of material yield 
different results. As will be seen in the course of this paper, 
this difference may be ascribed to the fact that the genei’al 
effect of Sacculina on Carcinus is far less marked than it 
is on Inachus, so that we might expect the same to be true 
of the effect of the parasite upon the blood-properties of its 
hosts. 
The blood of Carcinus exhibits three chief types of 
variation with respect to colour; it may be pale blue, owing 
to the presence of haemocyanin, in which case it may be 
spoken of as non-pigmented or colourless; it may be of a 
salmon-pink colour owing to the presence of the lipochrome, 
tetronerythine, which masks the blue colour of the haemo- 
cyanin, or it may be yellow owing to the presence of a 
different lipochrome, which may be called lutein. The 
presence or absence of these substances in the blood follows 
certain definite phases of the animal’s existence. The blood 
is invariably colourless or practically free from lipochrome 
immediately at and after a moult, and also in the case of the 
female after the eggs have been shed to the exterior. It 
