THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBARUS 17 



The fixation of the chelae was a gradual process ; at first the claws of the 

 chelae were not opened even when those of the walking legs were opened and 

 shut, but soon the chelae claws opened and shut and soon seized hold of any 

 solid object accessible. Sometimes the object seized was again let loose but be- 

 fore long the chela? had reached in among the mass of young and eggs far- 

 enough to find and fix upon one of the egg stalks, which are of a material and 

 size seemingly well fitted for the attachment of. the claws. Henceforth the chela? 

 seemed to remain always fast and their structure as described below indicates 

 that once imbedded in the material of the egg stalk the tips of the claws could 

 scarcely be liberated by the crayfish. This fixation was first made out in the 

 English crayfish by Huxley ('80), who inferred that when once fast it would 

 be difficult, or impossible, for the claws to open again. 



This use of the chelae to obtain attachment to the mother was exercised 

 with what appeared to be very earnest effort and once successful it was found 

 that the telson thread was soon ruptured. And then if the larva? were dis- 

 turbed they flapped their abdomens up and down and it was seen that the tel- 

 son thread had broken so that a piece of it was still attached to the telson and 

 was waved about by the telson like a bit of rag fastened to it. Henceforth the 

 young held fast by the chelae only. 



The general appearance of this mass of young on the mother was peculiar 

 since the rounded head-thorax was the chief part visible in each and this was 

 of light color with a striking bilobed or horseshoe-shaped, dark red, yolk mass 

 across it. The legs and abdomen were concealed and the dark eyes were gen- 

 erally out of view. With bent heads and outstretched limbs their attitude 

 ludicrously suggested one of supplication. 



Thus they remained for some days. When disturbed the young made tramp- 

 ing movements with their legs but did not move from the place to which they 

 were fixed by their long chela?. The abdomen, carried down under the thorax 

 somewhat as in the embryo, was not readily moved but with sufficient stimulus 

 from a needle point was flapped rapidly back and forth. When a larva was 

 forcibly pulled off from the mass its chela?, still attached, were stretched out to 

 their fullest extent and when the larva was released the chelae contracted and 

 made the larva spring back into place where its limbs and abdomen were again 

 drawn in under the thorax and the creature became again one of the herd of 

 "bison" presenting only their humped backs to the observer.' If by stronger 

 pulling the larvae were torn loose from the mother the chela? parted from the 

 egg stalks without breaking and reaching about seized hold of adjacent objects 

 such as the antennae of other larvae. Left to themselves on the mass, these 

 separated larvae soon got back again amongst the crowd ; but if put upon the 

 bottom of the dish they did not yet stand up but only gyrated about by flap- 

 ping their abdomens. 



