THE YOUNG OF THE CRAYFISHES ASTACUS AND OAMBARUS 11 



111 captivity slieddiiig, or ecdysis, took place iu early Hiimmer, iii some; thus 

 on June 11, when the water had risen from 9° C. in March to 22° C, one large 

 male cast its shell as one perfect piece containing- also the "teeth" and other 

 part of the lining of the "stomach." The creature was then quite soft and 

 easily indented by touch upon its carapace; it lay inert but could be made to 

 crawl iu a somewhat palsied way and even to flap its abdomen. On each side 

 of the heart region the carapace bore a white, indented, scar, as if made by 

 the claws of some other crayfish, so that the advantage of concealment at this 

 season as practiced by other Crustacea doubtless applies here as well. Thi' 

 entire shell was covered by a slimy soft mucus and its colors were brighter than 

 before, the under side of the legs showing also more blue. As seen from be- 

 low, the flesh of the abdomen had a peculiar coagulated appearance. 



The new carapace had a length of 57 mm. and the old of 43 mm., and had 

 enlarged in diameter from 25 to 28 mm. The cast shell had one broken, antenna, 

 53 mm. long, which was replaced in the new shell by a perfect antenna 68 mm. 

 long. A week later this crayfish was active and keenly seized and ate a large 

 lumbriculus. 



Two more males cast their shells June 15 and one of them was attacked 

 by others when only the carapace had been shed and the abdomen was as yet 

 in its old shell; one-half of the thorax and part of the abdomen were de 

 voured. The other large crayfish was able to flap its abdomen vigorously wliea 

 lifted out of the water though its body and clielie were soft and flaccid. Te. 

 both cast shell and new one the rostrum was broken off and had evidently not 

 been regenerated. Still another large male, received in October, 1904, cast its 

 shell May 19, 1905, and could move about thotigh still soft. 



The breeding season of these crayfish was far advanced when they were 

 received in February. In many cases the males had no sperm left in the defer- 

 ent ducts and the females had laid their eggs, which in four dead and six live 

 specimens formed large dark masses attached to the abdominal limbs, or pleo- 

 pods, and to the sternal hairs of the abdomen. Contrary to expectations, these 

 eggs were still alive and it was found possible to rear them and to get the sub- 

 sequent stages in the life history as described below. In the hope of getting 

 light upon the early part of the breeding season, another lot of thirty-seven 

 crayfish of the same species were got from the same place October 29, 1904; but 

 here again the beginning of the breeding season had passed. The only two sur- 

 vivors on arrival were both males, and three others recently dead were also 

 males, so that here again the vitality of the males seems to exceed that of the 

 females. In all there were twenty-two males and fifteen females. Five of the 

 females had eggs upon the i)leopods and these were in early cleavage, showing 

 some twenty nuclei migrating to the surface. It would thus seem that egg-lay- 

 ing takes place in the autmnii, )ir(ilinl)ly in O'-tober, and subsequent observations 



