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THE AMERICAN NATURALIST [Vol. XL 



the period of extrusion and six minutes after "turning" had 

 begun, when an undisturbed female was taken out of the water 

 many of the eggs in the chamber ran over from side to side and 

 tended to escape at the angle between the abdomen and the thorax 

 on each side. Some of the eggs were then loosely attached to the 

 pleopods, but when the abdomen was forcibly straightened out 

 and held downward many of the eggs glided off over the end of 

 the telson. 



Though the details of action of the female at the time of extru- 

 sion of eggs were different in other cases the following special 

 case is thought to be, in the main, typical. A crayfish lying upon 

 its back with the telson so far forward over the thorax as to reach 

 to the posterior edges of the second legs showed no movements 

 of any organs for a minute and then only a slight motion of the 

 antennules and of some legs. After four minutes more there 

 were some slight movements of the third legs and of the left chela. 

 The right chela rested upon the bottom of the dish and so held 

 the animal in more stable equilibrium. By this time the slow 

 relaxation of the abdomen had let the telson glide so far back 

 that the bases of the third legs were nearly uncovered. Three 

 minutes later by looking in under the telson one could see eggs 

 coming out of the openings of both the right and the left oviducts, 

 which openings are upon the bases of those legs. 



Where the tail-fan had been over the thorax, as far forward as 

 the cheliB, there was left a layer of glaire. On counting the eggs 

 in the issuing streams, still three minutes later, they seemed to 

 come out at the rate of one a second on each side. The only 

 movements of the animal were a temporary fanning motion of an 

 exopodite near the mouth. But five minutes later the animal had 

 turned to lie with the left side somewhat elevated and the eggs 

 were seen falling out of the oviduct of that side across the body 

 then to glide back into the abdominal basket. A minute later 

 they were coming out at the rate of ten in sixty-five seconds, in 

 groups of two or three at one jet and then an interval before the 

 next row of two or so. In another minute there were signs of 

 life in the rapid fanning of exopodites on the left of the mouth, 

 which continued for a minute, nearly stopped, and then started 

 again. After a minute more there were added a rolling of the 



