10 THE YOUNG OF THE CRAYFISHES ASTAGUS AND CAMBAKUS 



It was decided that this Astacus was probably Astacus leniusculus Dana 

 as distinguished from A. Trowbridgii by Faxon ('85) and the following observa- 

 tions upon their habits in captivity seem to be all that is known of this species, 

 beyond its specific -characters. 



The largest specimen was a female measuring 155 mm. from tip of rostrum 

 to end of telson, 205 mm. from tip of chela to tip of telson, 40 mm. wide across 

 the thorax and 35 mm. deep; the abdomen was 45 mm. wide and its tail fan 

 expanded to a width of 70 mm., exclusive of the setae. With only about one-half 

 of its eggs left upon its pleopods this female weighed 106 grams. 



The smooth clean shells and large well colored claws gave these crayfish 

 an attractive and decidedly lobster-like appearance, which was enhanced by 

 their very active pugnacious nature. In shallow water they quickly responded 

 to approaching objects and readily threw themselves into a defensive attitude, 

 leaning back with the whole anterior region raised high from the bottom of 

 the tank, thrusting their brilliantly colored claws above them high into the air 

 and either holding them wide apart and open or clashing them together towards 

 an approaching object, towards which they lunged, or even seemed to spring. 



Their quickness to react to distant objects, their quick reflexes and irrita- 

 bility led me to suppose they might well be carnivorous and their clear colors 

 suggested a life in clear water, but the collector reported that the Willamette 

 River, whence they came, was a rather muddy stream, though formerly used as 

 water supply for Portland. In captivity they were nocturnal, lying quiet and 

 away from the lighter parts of the tank in the daytime and crawling about in 

 the night. They sometimes injured one another and also ate parts of their dead 

 fellow-crayfish and, as is so common with many kinds of crayfish, there were 

 cases of regeneration, which may have followed from injuries caused by their 

 pugnacious and carnivorous habits. One male 95 mm. long, when received, had 

 two regenerating limbs. The left chela was represented by its original basal 

 two segments and by a delicate new limb only 9 mm. long protruding from the 

 truncated end of the second large segment. This little, bluish protuberance 

 was made of six movable segments and it was movable upon the* old limb 

 whence it sprang, so that to make the seven normal movable segments of a 

 complete limb a reduction in the number of movable joints must take place, 

 probably by the base of the new growth ceasing to move upon the old second 

 segment. The other regenerating limb was the third left walking leg and here 

 again the old second segment bore a soft protuberance, which, however, was as 

 yet not segmented. Thus in this Astacus, as is common in other crayfish, re- 

 generations had started from the preformed breaking plane, and in handling this 

 same specimen, though dead, the right third walking leg fell off at the breaking 

 plane. 



