STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 585 
carida, the hermaphrodite individuals are at first, in the larval 
state, apparently pure males. They then settle down as 
parasites and lose every trace of their male organisation and 
become converted into what are apparently pure females. In 
fact for a very long period of time they were considered by 
naturalists to be typically dioecious animals with very marked 
sexual dimorphism. Now let us suppose that for some reason 
or other certain of these individuals failed to develop further 
than the male larval state. They would then be constitution- 
ally hermaphrodites, in which the male condition was dominant, 
and they would be put down as males. Then let us suppose 
that other individuals for some reason left out the male period 
of their history, possibly by becoming fixed parasites at an 
earlier period before the testes were developed. These indi- 
viduals would then be constitutionally hermaphrodites, in 
which the female condition was dominant, and they would 
be considei’ed with equal confidence as females. In this way, 
by shifting the period at which the sexual organisation 
matures, a process which may be very easily conceived to 
occur, we would arrive at an apparently complete reversal of 
dominance. 
That this shifting of the period of maturity actually occurs 
is shown by the existence of the three classes of hermaphro- 
ditism noted above ; thus in the single class of simple Ascidians 
we meet with both protandry and protogyny. Let us take 
another slightly different instance, the case of the spider crab 
Inachus, parasitised by Sacculina. The male parasitically 
castrated crabs may show every degx’ee of modification towards 
the female state, until finally we obtain male crabs which have 
been so completely transformed as to retain only a single male 
character, viz. the copulatory style in so i-educed a state as 
to be invisible except with a lens. These crabs, besides 
exhibiting in a typical condition the broad abdomen, reduced 
chelae, and abdominal swirnmerets of the female, may under 
certain conditions develop ova from the remains of their 
testes, and these ova may grow to a very large size and 
become filled with the reddish-coloured food-yolk character- 
