COXJUGATIOX IX THE CRAYFISH, CAMBARUS AFFIXIS 245 
The greater size and especially length of the chelae of old males 
seems directly connected with this function and it is noteworthy 
that the chelae so nicely encompass all the ends of the claws and 
walking legs of the female. 
However, it is not necessary for the completion of conjugation 
that all the claws be held. Some ma}' escape the normal male 
and a male with but one chela can hold the legs of but one side. 
One male lacking claws on both first and second left legs held in 
conjugation a female lacking the same claws on the right, but 
with the one chela of the right the male held all the claws that 
remained on the left of the female. 
Experiments would be necessary' to determine the true nature 
of this habit of claws-clasping. When some female claws are left 
free they have been sometimes seen to pinch parts of the male. 
Mounted thus upon the female, the male is held in position 
not only by the two chelae but by the contractions of other legs 
that are wrapped, as far as their rigidity permits, about the con- 
vex thorax of the female. There remain but few legs that stand 
out right and left from the male and prop the body from falling 
over, fig. 1. As the back of the female is rounded the conjugating 
crayfish tend to roll over onto the side, but this is resisted by the 
male legs that act as props. But while the conjugation is com- 
monly carried on with the male in the normal position of loco- 
motion and the female in the forced, inverted position that cray- 
fish assume only under compulsion (except at the period of egg- 
laying), it frequently happens that the pair lie upon their sides. 
When the water is so shallow that it will not cover the male as 
above mounted, the pair may lie upon the side, and thus conju- 
gation was carried out in water too shallow to cover even one 
animal. 
But before the firmest clasping of the female the male must 
erect the stjdets, cross the fifth leg and attach the hooks. These 
three acts take place as follows : 
When the male has seized all the claw-legs of the female in his 
two chelae he moves back and up away from the female, still 
holding the claws, and then raises the organs that are to transfer 
the sperm. These are the first and second appendages of the 
