THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBAEUS 51 







which to hold, or kicking their legs about, swinging their pleopods and flap- 

 ping their abdomens formed an animated restless mass quite unlike the inert 

 one seen in the previous period. Thus active, though holding fast, the larvae 

 were no longer densely crowded in close to the pleopods as in the first stage (fig. 

 52), but loosely aggregated (fig. 70). 



The old larval cases shrivelled and not readily recognizable as more than 

 crumpled membranes, still remained fast by their chelae and the old egg cases 

 were yet fixed by their stalks to the maternal pleopods. Side by side on old 

 egg stalks were the pairs of living claws and the empty cuticles of old cast off 

 claws. Thus the second larvae lived amidst a mass of former envelopes, the 

 ghost-like phantoms of their former selves and the rigid cradles of those selves. 



While many larvae holding fast to the pleopod hairs and to egg stalks tend 

 to pull themselves in close to the pleopod so that they become buried amongst 

 the egg stalks and empty cases, a few larvae at the periphery of the mass may 

 dangle free in the water, as in the lower right corner of figure 70. These are 

 larva; which have recently cast off the first cuticle and are still in a soft, help- 

 less condition. Before these larvae succeed in reaching up and seizing hold of 

 some part of the general mass they are in danger of falling to the bottom where 

 they might be lost, though when they are removed it is found that they can stand 

 and walk, with difficulty. However they seem strongly controlled by an instinct 

 to climb, crawling over one another in heaps when removed from the mother and 

 swimming only when thrown into Perenyi's liquid and possibly many would 

 eventually climb up onto the mother. At all events they are prevented from fall- 

 ing away from the mother by a fine thread which, as indicated in figure 70, 

 passes from the posterior end of the larva to the crumpled, cast-off cuticle 

 which still is firmly fixed to the mother. This thread may be called the anal 

 thread since it actually conies from the anus and not from the rim of the telson 

 as did the supporting thread of the first larva. 



But before discussing this anal thread some general features of the second 

 larva may be considered. The abdomen is still carried bent down as seen in 

 figures 69 and 68, but the cephalothorax is more elongated and narrow than in 

 the first stage and ends in a sharp pointed toothed rostrum that projects out be- 

 tween the eyes and is only slightly bent down. The legs are longer and may now 

 be used for walking and the antennae stand out in front of the animal as if use- 

 ful feelers, in strong contrast to their apparently useless position in the first 

 larva (fig. 50). This increase in length and change of position of the antennae 

 gives the mass of young in the second stage (fig. 70) a much more living aspect 

 than was possible in the first stage (fig. 52). The abdomen when straightened 

 out is seen to end still as a simple rounded telson (fig. 71) with the large sixth 

 pleopod still within it on each side the anus and with a terminal part that has 

 its middle lobe set off but slightly from the side lobes. The edge of the telson 



