8 
A. D. Darbishire. 
a profound change. The males, which are characterised by swollen 
chelae, narrow abdomen and copulatory styles, change into a 
hermaphrodite condition by acquiring characters peculiar to the 
female, to wit, broad abdomen with swimmerets and smaller and 
weaker chelae; indeed the male is, in its extreme condition, to be 
distinguished from the female only by the presence of copulatory 
styles. The female, on the other hand, very rarely loses its sexual 
characters and never acquires any of those peculiar to the male. 
Smith has examined the reproductive organs of infected crabs in all 
stages, and has found that if the crabs recover from the effects of 
the parasite (which they often do) the male may produce both 
mature sperms and mature ova in correlation with its acquired 
secondary sexual characters ; but that the female produces ova only. 
Potts 1 has observed similar phenomena in other species of crabs. 
Seeking to interpret these changes, Smith makes the suggestion 
that the sexual characters may depend not upon a differentiated 
reproductive organ, but upon a sexual formative substance which is 
defined as “a product of the general metabolism of the body which 
differs characteristically in the male and female.” The parasites of 
the crabs interfere with the metabolism, whose product, the sexual 
formative substance, becomes changed, “causing in the female 
atrophy of the gonad and of the secondary sexual characters, in the 
male a passing from the highly differentiated male condition to the 
more generalised hermaphrodite state.” 
Smith does not ignore the indications of recent research, 
namely, that sex is probably fixed in the zygote: for he holds that 
“a legitimate distinction may be drawn between the presence of a 
metabolic substance in the body capable of assuming activity under 
the proper stimulus, and a transmission of a sexual potentiality 
which may depend on some quiescent structural element incapable 
of activity except after the elaborate and mysterious changes which 
accompany the inception of a new generation.” Indeed he suggests 
that the male in these cases may be heterozygous for sex (DR) 
with maleness dominant, and the female a homozygous recessive 
(RR). Following up the idea that it is only the male which contains 
the potentialities of both sexes, Smith draws attention to the almost 
universal occurrence of protandric hermaphroditism in animals 
which have become secondarily hermaphrodite. This phenomenon 
is accounted for if it be assumed that, owing to a change in the 
habits of life, the sexual organs have undergone degenerative 
1 Potts, Q. J. M. Sc. Vol. L., pp. 599-621. 
