260 
GEOFFREY SMITH. 
that tlie presence of Sacculina profoundly influences these 
properties, but the effect is different in the case of Inachus 
and Care in us, and presents features difficult to interpret in 
both. 
Robson has made the remarkable discovery that in 
Inachus the infected individuals of both sexes show the 
presence of lipoclirome in the blood with about the same 
frequency as normal females that are maturing their eggs, 
i.e. in respect of the proportion of individuals showing 
lipochrome in the blood the infected animals of both sexes 
are in a category which agrees most closely with the breed- 
ing females. Now this observation appears to be a complete 
vindication of the theory which I put forward last year, that 
the infected individuals would be found to be elaborating a 
yolk substance similar to that which the female deposits in 
its ovary at maturity. But there is a puzzling feature in 
Robson’s discovery, and this is that the lipochrome present in 
the infected crabs is always of the pink tint that is usually 
associated with the normal individuals soon about to moult, 
and not of the yellow colour characteristic of the female. It 
must be admitted that this fact is b,oth unexpected and 
awkward; it may, however, admit of the following interpre- 
tation. The presence of the pink lipochrome at any rate 
indicates a higher percentage of fatty material in the blood, 
and this is in support of the theory ; the pink lipochrome is 
very probably only masking a considerable amount of the 
yellow lipochrome, but why should the pink be there at all ? 
Now one of the effects of Sacculina on its host is to prevent 
it moulting, after the Sacculina has once come to the 
exterior. Consequently the infected crabs are not able to get 
rid of the red lipochrome at the moult in the ordinary way, 
and we might expect that au accumulation of this substance 
would take place in the blood. 
Turning to the effect of Sacculina on Carcinus, we find 
on the contrary that the blood of infected individuals is 
invariably either colourless or else slightly yellow. We 
never get any perceptible development of the pink pigment, 
