264 
GEOFFIiEY SMITH. 
phenomenon of “ parasitic castration” was merely an un- 
accountable curiosity, it now falls into place with other facts 
of female sexual organisation, and is to a great extent 
intelligible. 
Summary. 
(1) The blood of Carcinus maenas exhibits three chief 
conditions — colourless, pink, and yellow — the pink and yellow 
colour being due to the two lipochrome pigments, tetron- 
erythrin and lutein. The pink colour appears in individuals, 
especially in males, which are approaching the period of a 
moult, the yellow is characteristic of the female when the 
ovary is approaching maturity. 
(2) An estimation of the fat content of the blood, by 
means of saponification and extraction of the fatty acids, 
gives the following average numbers: for colourless blood 
*059 per cent., for pink blood ot‘ males *086 per cent., for 
yellow blood of females *198 per cent. Thus the breeding 
females are shown to possess an excess of fatty material in 
the blood, and the yellow lipochrome is seen to represent a 
higher fat value than the pink. 
(3) Beside the blood, the “ liver ” also exhibits periodic 
variations in the amount of fat present, fat being sometimes 
present as 12 per cent, of the total weight, sometimes as low 
as 4 per cent. The females maturing their ovary and having 
yellow blood always have a large proportion of fat in the 
liver. 
(4) Crabs of both sexes infected with Sacculina also 
always show a large supply of fat in the “ liver.” In the 
case of Carcinus the blood of infected individuals is either 
colourless or pale yellow, but in the case of Inachus the 
blood becomes charged with lipochrome, as the result of 
infection, though this lipochrome always shows the presence 
of the pink colour as well as the yellow. 
(5) The difference in reaction of the blood in the two 
cases is explained as consistent with the small effect which 
