28 THE YOUNG OF TUB CRAYFISHES ASTACl'S AXD CAMBAKUS 



opods clean but still occupied by the larv*. In the Astacus in France Chan- 

 tran (71) finally convinced himself that the larva? ate their cast skins and the 

 egg capsules; and the same probably occurs in Astacus leniusculiis. 



The habits of the second larvje showed much greater diversity than was 

 possible in the attached larvae in the first stage but through the early part of 

 the second stage a tendency to climb seemed a dominant feature of their lives. 

 AMicn a number were put into a dish by themselves they tended to climb up onto 

 one another to form a nuiss but if put back with the mother they soon climbed 

 up onto her pleopods where they held on so firmly that when a pleopod was cut 

 off and thrown into 70 per cent alcohol, some of the larvae still retained their 

 hold though most of them did not. When the ]arva> alone were in a dish with 

 a spray of iii\ ridpliylhuii they climbed up it and ci-awled together in a mass 

 between the ])hmt and the glass; but thej^ did not climb up onto a piece of 

 cotton cloth hanging down in the water from a floating cork. Even when the 

 mother was dead, the young twenty hours after passing into the second stage 

 continued to hold firmly to the maternal pleopods. But after three more days 

 the young lijul ceased to huddle together so much, and crawling altout over the 

 bottom of the ;if|uai-ium, and sometimes swinuning, they were at times carried 

 away with tlie current of water. Though some of the larv;p concealed them- 

 selves under ooze and dead leaves at this time, others continued to hold on to 

 the abdomen of the dead mother for four or five daj^s, when the abdomen was 

 cut off and fastened at the surface of running water, but about May 18 these 

 larva^ also dropped to the bottom and lived there. This climbing instinct can 

 then be satisfieil in various ways, and when thirteen larv» were removed and 

 put into a dish with another female bearing young, but few minutes sutficed 

 for five of the thirteen to find and to climb up onto the pleopods of the strange 

 female. The i)ossibility of resolving these habits of the young second stage 

 crayfish into so-called tactic phenomena, into chiefly geotactic and stereotropic 

 responses, will be considered in connection with some observations upon the 

 young of Cambarus. 



The general form of the second stage as represented in figures 2.3 and 24 

 is obviously more like the adult than like the first stage as is true also of the 

 habit. Comparing these figures with 3 and 4 there is a noteworthy change in 

 size; after casting off the first skin the crayfish measured 11 mm. from tip of 

 rostrum to end of telson, exclusive of the long fringe of plumose set:^ which 

 made the length 12 nun. if the setse were included, and so greatly enlarged the 

 area of telson available for locomotion. The thorax was 2 mm. wide and about 

 2.5 mm. deep. The cephalothorax was 6 mm. and the abdomen 5 mm. long; 

 the telson was 2 mm. wide without the set;e, and 4 nmi. with the sets. The an- 

 teniiM' were 10 mm. and the cheLu 8 mm. long. All these measurements were 

 tnken fi-om preserved material and show that the animal was now a large larva. 



