THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBARUS 59 



Possibly the restricted artificial conditions both prolonged the duration of 

 association of mother and young and lessened the variety of external stimuli 

 so that there was a certain amount of domestication. By close confinement 

 and by supply of abundant food to be given the mother and. young without 

 effort on their part, it would appear possible to make of the crayfish a domes- 

 ticated animal with a more prolonged association of mother and offspring. Such 

 experiments would build upon the ground that the crayfish is preeminently a 

 creature in which embryonic life has been continued on as a series of stages, 

 ancestrally free, but now dependent upon the mother and with special organs to 

 ensure that dependence. 



The young that came down from the pleopods took food and eagerly de- 

 voured fragments let loose from the mouth parts of the mother when she was 

 feeding. At such times the young climbing on the mouth parts of the mother 

 seemed in danger from those rapidly vibrating appendages but always seemed 

 to be shoved aside and not devoured. When a couple of tubifex were put into 

 the water and seized by a female, the young also took hold and either car- 

 ried off pieces or continued to hold on while the worm was being dragged into 

 the mouth of the female. Thus the young were drawn up with the food to the 

 mouth of the female, but when between the maxillipeds the young leaped away 

 and none seemed to be injured. 



The accompanying illustrations (figs. 92 and 93), being from photographs 

 of living crayfish in water but poorly represent the pinkish mass of active 

 larvje crowding under the abdomen of the mother or the separate young climb- 

 ing over the back of the mother or walking about in the dish. They serve, how- 

 ever, to show the crouching attitude of the mother, the size of the young in this 

 third stage and the general character of this active dependence of young upon 

 mother which was long since admired by Roesel von Rosenhof (1775), and might 

 be likened to the clustering of hen and chicks or of sow and pigs. Roesel von 

 Rosenhof 's statements regarding the association of the young and parent As- 

 tacus are as follows : 



"Wenn die Mutter dieser kleinen Krebse, nachdem selbige sich zu bewegen 

 angefangen, zuweilen bei ihrem Futter stille, oder sonst ruhig sitzet, so be- 

 geben sich solche von ihr etwas weg und Kriechen urn zie herum; merken sie 

 aber nur im geringsten etwas feindliches, oder sonst eine ungewonliche Bewe- 

 gung im Wasser, so scheinet es, als ob sie die Mutter, sich zuruck zu begeben, 

 durch ein Zeichen erinnerte; indem sie allezusammen geschwind unter den 

 Schwanz zuruck fahren, und sich wieder auf einen Klumpen zusamensetzen, 

 worauf sich die Mutter sammt selbigen mit mogligster Eilfortigkeit, in Sicher- 

 heit begiebt, welche sie aber etliche Tage darauf , nach und nach verlassen. ' ' 



The suggestion of a possible signal to recall the young raises the question 

 as to the nature of the means by which the young associate with the parent. 



