104 CRUSTACEA CHAP. 
tionately much more highly developed than in the low males. 
The only difference between the two cases is that whereas in 
the beetles growth ceases on the attainment of maturity in the 
low degree, in the Crustacea the low male passes through a 
period of growth and sexual suppression to reach the high 
degree of development. 
The condition of the middle-sized males may be looked upon 
as one of partial hermaphroditism, indications of the female 
state being found in the flattened chelae and in the reduced 
state of the testes. This interpretation is greatly strengthened 
by the state of affairs observed in the life-history of the male 
Sand-hoppers, Amphipods of the genus Orchestia.' In the young 
males of several species of this genus, at the time of year when 
they are not actively breeding, small ova are developed in the 
upper part of the testes of more than half of the male individuals, 
these ova being broken down and reabsorbed as the breeding 
season reaches its height. Nor is this phenomenon confined to 
this genus; in the males of a number of widely different 
Crustacea these small ova are found in the testes at certain 
periods of the life-history (e.g. Astacus*), when the animal is not 
breeding. 
The foregoing facts indicate unmistakably that the males of 
a number of Crustacea under certain metabolic conditions, 7.e. 
when a stage of active growth as opposed to a stage of re- 
productive activity is initiated, alter their sexual constitution in 
such a way that the latent female characteristics are developed, 
and the organism appears as a partial hermaphrodite. In the 
preceding paragraph we saw that the males of a number of 
animals, especially Crustacea, react to the metabolic disturbance 
set up by the presence of a parasite in exactly the same way, 
z.e. by developing into partial or total hermaphrodites. From 
these two converging bodies of facts we may conclude, firstly, 
that sex and metabolism are two closely connected phenomena ; 
and, secondly, that the male sex is especially hable to assume 
hermaphrodite characters whenever its metabolic requirements are 
conservative, assunilatory, or in a preponderating degree anabolic, 
as when a phase of active growth is initiated, or the drain on 
the system, due to the presence of a parasite, 1s to be made good. 
1 C, L. Boulenger, Proc. Zool. Soc. 1908, p. 42. 
2 Garnier, C.R. Soc. Biol. liii., 1901, p. 88. 
