178 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



along one free edge. At one of the angles of the penultimate 

 segment there is a group of strong picks that look like the 

 horny tips at the ends of legs. In fact these two picks are born 

 upon a truncated process that suggests a homology with the 

 finger of the chelate legs, that process of the penultimate 

 segment which apposes the last segment to form the claw; 

 and we might regard this fifth leg as having lost, or not yet 

 acquired, a perfect claw. The penultimate segment also bears 

 beautifully serrated hairs, as indicated in the figure, recalling the 

 appearance of some setae of annelids. That these tufts of ser- 

 rated hairs may serve as scouring brushes seems not improbable. 

 We would then have a double pick to loosen dirt, a stiff comb 

 and a brush with saw-tooth hairs to accomplish the cleaning. 



The fourth leg has the same structure and though it was not 

 seen in use it may well take part in cleaning. The second and 

 third legs bear well developed claws and these were seen slowly 

 plucking at the encrusted abdominal surface. As elsewhere 

 shown ^ these claws are well fitted for cleaning as they can pick 

 off objects and are provided with a long row of flat, serrated 

 plates on each limb of the forceps that should serve excellently 

 in cleaning the pleopods. 



Time of laying. — In confinement the crayfish deposited their 

 eggs at night time with few exceptions ; only one among thirty- 

 two laid eggs in the day time. Yet it was found possible to force 

 the laying of eggs in the day time by keeping the female every 

 night in barely enough running water to moisten the ventral 

 surface of the body and with no opportunity for the normal 

 submergence. When returned to deeper water in the day time 

 eggs were finally laid, at noon, upon the third day of such 

 treatment. 



Laying. — The females were easily disturbed and never laid 

 when under observation so that the actual emission of eggs was 

 not seen but the following facts were observed just before 

 and just after the actual laying. A short time before laying 

 the female is sometimes found lying upon her back waving 

 the abdominal appendages back and forth in a rhythm of about 



