50 
GEOFFREY SMITH* 
charged with yolk or fat materials which simultaneously 
affect both ovary and comb. 
Now this is exactly the process which we deduced as 
occurring in the spider - crabs attacked by the parasite 
Sacculina, which assume adult female characters owing to 
the circulation in their blood of yolk materials similar to that 
which is stored by the normal female crab in its ovaries at 
maturity ( c Quart. Journ. Micr. Sci./ vol. 55, p. 233). The 
parasitised crabs, both male and female, do not possess an 
ovary, but the Sacculina forces them to elaborate the yolk 
material, and the presence of this substance in the blood acts 
as the stimulus for the development of the adult female 
secondary sexual characters. 
It is of considerable interest to find such closely parallel 
facts in such widely different animals as Crustacea and birds. 
In both cases we find that the stimulus for the development 
of secondary sexual characters does not emanate from the 
ovary, but that it consists in the presence of fatty materials 
in the blood elaborated elsewhere and in process of being 
conveyed to the ovary. That the seat of formation of this 
fatty material is the liver occurs to us ns a natural hypothesis, 
and it will be fully substantiated in succeeding studies. 
Summary. 
(1) The rapid and marked increase in area of the hen’s 
comb is proved both in adult and young hens to occur 
simultaneously with the periods of egg-laying. 
(2) This increase of the comb in the hen is due to a fatty 
infiltration of the central connective-tissue core of the comb; 
the decrease in the comb is due to the abstraction of the fat. 
The cock’s comb only contains small quantities of fat com- 
paratively in the central core, the substance of the comb 
consisting principally of fibrous connective tissue. The cock’s 
comb does not exhibit marked fluctuations like the hen. 
(3) The increase in the comb is not accompanied by a rise 
in general body-weight, though such a rise usually occurs 
some time before the increase and fat deposition occur. 
