1 68 BULLETIN OF THE BUREAU OF FISHERIES. 



It is dependent upon a complicated chain of events, which suggests the story of the old 

 woman who went to market to buy a pig. Thus if the egg stalk in Astacus does not 

 adhere to a "hair" of the parental swimmeret or to another egg; if the two egg shells 

 are not themselves adherent; if a certain deUcate thread, which is spun, as it were, 

 from an embryonic cuticle shed at hatching time, does not itself stick on the one hand 

 to the telson of the young and on the other to the inside of the inner egg shell, and thus 

 tether the little one to its mother; if again, a little later, when its leading string has 

 broken, this young one has not been enterprising enough to hook on to some part of 

 the egg glue with its great forceps, the tips of which have been bent into fishhook form, 

 it comes to certain grief. The result is fatal at whatever point the chain weakens and 

 snaps. 



A few hours after hatching, the helpless little crayfishes, still dangling from the 

 "telson threads" which secure each to the parent, begin to flap their abdomens and to 

 open and close their big, hooked claws. In this way they manage to seize the old stalk 

 of the egg and, with hooks embedded in its tough chitinous "glue," they hold on, liter- 

 ally for dear life, often grasping the same stalk with both chelae. 



At the second molt this crayfish is for the first. time free, and soon begins to descend 

 the parental pleopod, climbs over its mother's body, and makes short excursions in the 

 neighborhood, returning again and again to the alma mater and the family brood. 

 Hitherto it has been sustained solely by the generous amount of yolk inherited from its 

 egg state, but since the egg stalks and cases, as well as the cast-off skins, which were 

 attached to the mother, disappear at this time, it is thought that they are eaten by the 

 young and constitute the first direct food they receive before beginning to forage for 

 themselves. 



In Astacus the "telson thread," according to Andrews, represents an embryonic 

 molt or cuticle, arid the abdominal part is turned inside out at the time of hatching 

 and drawn out into the thread, the cuticle sticking on certain of the median marginal 

 spines of the telson. The newly hatched Cambarus is tethered to its mother in a some- 

 what similar way by means of the partially inverted and telescoped "lost larval cuticle," 

 which is shed at hatching and is in this instance an "anal thread," since it sticks at two 

 points only — on the side of the mother to the egg membranes, which are adherent to 

 her, and on that of the young Cambarus to a portion of the intestine where its cuticular 

 lining is at first set free. As a result of the tension this embryonic molt is stretched 

 and crumpled, with a tendency to turn the abdominal part inside out. This telescoping 

 and partial inversion of the discarded cuticle is checked only by the molted plate of the 

 telson, with the resultant production of a narrow creased ribbon, the "anal thread," 

 which is firmly fastened to the intestinal wall. 



