60 THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBARUS 



The interrelation of mother and young in the crayfish would seem a profit- 

 able field for study of comparative family life and the following few facts sug- 

 gest lines of inquiry. 



It is not evident that the mother gets any advantage from the clinging of 

 the young to her body, though if in the third stage they eat off the old egg stalks 

 and cases, the cleansing of the pleopods so caused might satisfy in the mother 

 something akin to whatever it may be that causes her to laboriously cleanse that 

 region just before the eggs are laid; but judging from the long endurance 

 of the load of eggs and larvae and from the frequency of dirt and parasites 

 upon the pleopods it seems hardly probable that the female would feel an in- 

 stinct gratified when the pleopods are clean again. That the female is at all 

 conscious of the presence of the larvae remains to be found out by evidence not 

 yet at hand; however, when a lot of young were put into a dish with a male 

 and they climbed over him he cleaned them off from his abdomen and seemed 

 to be annoyed by their climbing over his head, but when the same young were 

 put with a large female that had reared her own young long enough and natur- 

 ally separated from them some weeks before, they climbed up onto her withoiit 

 her showing any evident sign of being affected by their presence upon her 

 chelae, thorax and abdomen. When a female was feeding and the young climbed 

 upon her chelae she did not seem aware of them but reacted eagerly to a tubifex 

 near her chelae. Whether, then, the young are simply tolerated, [as are the 

 small parasitic leeches over the body of crayfish,] as a continuation of the eggs 

 that are part of the body, or whether the females have special responses 

 to stimuli given by the young is not known, but the former seems not improb- 

 able. 



The young, on the other hand, act as if they were strongly affected by the 

 mother but this may be due to a few simple reflexes and without any complex 







visual or other conception of the mother's existence. At all events there is 

 no evidence that the young distinguish one female from another and when two 

 mothers were in the same dish some young of one climbed up onto the other. 

 Even when the young shaken off a female when they were in the third stage 

 were put in a dish with a female carrying her young in the second stage they 

 climbed up amongst the younger larvae of the strange female and seemed con- 

 tent. When the young were shaken off two females in separate dishes and the 

 females exchanged, the young climbed up onto the strange females ; in a few min- 

 utes all but three were upon one female and all but seven or eight upon the other 

 though she was moving about. Some young C. affinis in the second stage were 

 taken off from the mother and put with some young of C. Diogenes of the sec- 

 ond stage also removed from the mother and all were then put into a dish with 

 another female C. Diogenes bearing young in the second stage. All the young 

 got upon the foster mother and continued there, though the C. affinis were 



