STUDIES IN THE EXPEEIMENTAL ANALYSIS OF SEX. 595 
among the smaller and medium-sized individuals^ in which 
the chelse and abdomen have taken on the complete adult 
female appearance, the only male character remaining being 
the copulatory style, which is sometimes reduced to a minute 
knob (fig. 8). I was for a long time in doubt as to which 
sex these highly modified crabs belonged, as the majority of 
them on dissection proved to possess no remains of the gonad 
and gonoducts, except in certain cases some small shreds of 
germinal epithelium. In a few, however, the remains of the 
gonoducts were found, and in all cases they were in the 
position of the vasa defei’entia, proving the animals to be 
males in which the modification towards the female type had 
gone very far. Further reflection showed that all these 
highly modified crabs were originally males, and this was 
proved Avithout doubt by their invariable possession of the 
copulatory style in either a complete or greatly aborted state. 
For in the case of the females, although they, too, undergo 
characteristic changes, they never make any approach either 
in the chelae or abdomen towards the male state, and there is 
never any trace in them of the development of the copulatory 
style. 
It is therefore altogether impossible that other crabs, in 
which the sex cannot be determined by the internal gonad or 
its ducts, should be females which, contrary to all experience, 
had suddenly developed the single male character of the 
copulatory styles. That they were originally males, however, 
is shown by the perfect gradational series, which can be 
traced from hardly modified males up to those specimens in 
which the only male character retained is the presence of the 
copulatory styles. 
It is important to notice that the males, when they develop 
the female characters to any great extent, invariably exhibit 
these characters in the form in which they occur in the adult 
female, the abdomen assuming the trough-like appearance, 
and the appendages being slender and provided with filamen- 
tous hairs. I emphasise this point because certain people 
have argued with me that the modification of the male was 
VOL. 54, PART 4. NEW SERIES. 42 
