58 THE YOUNG OF THE CRAYFISHES ASTACUS AND CAMBABUS 



network of pigment cells on the tips of the chelae these areas appear conspic- 

 uously dark red. 



While the young in the third stage still remained on the mother for a while, 

 they were free to move about and soon became more and more independent. A 

 few hours after moulting some of the young were found walking about on the 

 bottom of the aquarium. When disturbed they leaped backward and. upward 

 several inches by strong strokes of the abdomen and looked not unlike shrimp, 

 while, when they walked, their habit of holding the anterior part of the body 

 high up in the water as well as the attitude of the slender chelae gave them 

 the alert, nervous look of shrimp-like creatures and made them look very unlike 

 the adult. 



The young climbed about on the pleopods of the mother, over her side and 

 back, upon her mouth parts and eyes and, though at first densely crowded under 

 the abdomen of the mother, more and more frequently they walked off to 

 greater distances, always returning to the abdomen if possible. The same 

 larvae that at times left the mother in the water, clung fast to her when she 

 was lifted out of the water. But by violently shaking the mother in the water 

 all the young could be shaken off. When two days after moulting into the third 

 stage some sixty larvas were thus shaken off and left in the same dish with her 

 all but twelve had returned to the mother's pleopods in twenty minutes. As 

 many as a hundred young were seen walking about the aquarium and climbing 

 up onto water plants for a time and later all but a few had returned to the 

 mother. 



At first, however, the young did not wander far from the mother and when 

 in a darkened aquarium the mother stayed in one spot for two hours the small 

 faecal casts of the young over the bottom of the aquarium were almost all very 

 near to the mother. 



In about a week this association of mother and offspring was gradually 

 given up and more and more of the young failed to return to the mother. 



In nature it is possible that the mother and young separate quite soon, 

 especially if the mother wanders about, but as yet nothing is known of the 

 natural life of this crayfish when carrying the young. It may be that the 

 female then lives in holes or cavities and then the young might long remain 

 with her. In captivity the females with eggs will dig holes in, the mud and live 

 in them as long as the water is well aerated, but come out when the water is 

 "not running. When kept in a small dish the female had no chance to escape 

 from the young and in some cases some of the young remained with the mother 

 and crawled over her three weeks and three days after leaving the egg, but 

 when such females were put into a large tank they walked away and hid them- 

 selves, leaving the young scattered about. 



