DACTYLOPUS. 109 
ing in mobility; the antenne clumsy, with their third 
and fourth joints short and thick, the second joint 
very long; the second foot-jaw ends in a strong, mas- 
sive, clasping hand; the first pair of feet are armed 
with doubly-curved claws; the feet, especially the last 
pair, are strong and clumsy, all the sete showing a 
tendency to become plumose. ‘The smaller and slen- 
derer breed has larger antenne, the third and fourth 
joints of which are much elongated; the prehensile 
apparatus of the foot-jaws and first pair of feet more 
slender, and there is also a much slimmer, slen- 
derer form of the limbs. In general structure and 
conformation of body, in the peculiar arrangement 
of sete, the serration of the abdominal segments, in 
short, in those points where distinct species mostly 
diverge, there is here a striking agreement. 
After diligent inquiry, these differences remained un- 
explained, and I was inclined to consider them as 
mere individual variations. But further investigation 
of all parts of the body convinced me that two distmet 
forms, with qualities diversely useful, had originated 
two separate races, one slender, swift, and agile, the 
other clumsy in figure, but robust and powerfully 
armed. ‘The two races are so far separate that inter- 
mediate individuals partaking of the characters of both 
are not met with.. The upper antenne, however, in 
each case show a tendency to similar variations; at 
the same time these variations are not so profound 
that they might not have been acquired singly or in 
combination. The differences in the relative size of 
the claws and prehensile organs may be traced back 
