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E. A. ANDREWS 
claws grasping all the claw legs of the female. The apparent 
absence of the fifth leg of the male is due to its being turned 
abruptly across between the male and female. Here it supports 
the styleyts, that are seen dimly, pointing forwards and down- 
wards from the abdomen of the male to the thorax of the female. 
Once the male is firmly fastened to the female the pair may be 
lifted out of the water without the male necessarily letting go or 
even showing any sign of being stimulated by the change in con- 
ditions. It is possible to separate the chelae of the male from the 
female and to bind them shut without stimulating the male to 
let go with the other limbs. External environment seems for the 
time to be concentrated in the crayfish of the opposite sex, as 
far as evident responses indicate action of environment. 
Before considering this process of conjugation in more detail, 
some consideration may be given the question as to how the male 
''recognizes" the female. 
In Cambarus affinis, as studied in the laboratory, the males 
will unite with the females during all the fall, winter and spring 
months, and if a male be kept in a small vessel till accustomed to it 
he will generally conjugate with a female introduced into the same 
vessel, usually very soon, but sometimes not for twenty-four 
hours, so that it is not always the advent of a new crayfish that 
stimulates the male to action. Observation of males and females 
under these conditions gave the impression that the male has only 
a vague stimulus from any crayfish at a distance, without any 
recognition of the sex at all. But once the male had seized another 
crayfish the result depended upon the sex of the crayfish seized; 
so that, in a sense, the male might be said to recognize the dif- 
ference between a male and a female after he had seized them. 
That is, the male seemed to act differently to males and females 
only after thay had been seized. And even then there was no 
evidence of any recognition of sex, except in the sense that the 
mode of reaction of the female made possible the carrying out 
of a chain of reflexes on the part of the male, which could not be 
the case if a male were seized. . 
Incidentally to other observations, Dearborn observed that 
a specially vigorous male, when blindfolded by a tin helmet. 
