16 THE YOUNG OP THE CRAYFISHES ASTACUS AND CAMBARUS 



measurements of preserved specimens : Length of head-thorax, 4 mm. ; width, 

 3 mm. ; depth, 3 mm. Length of abdomen, 5 mm. Length of antenna, 6 mm. 

 Length of chela, 5 mm. 



Eeturning to the account of the hatching young, it is to be noted that the 

 activities of the young were but slowly acquired; here and there amongst the 

 mass of eggs and young upon the female some larvae showed feeble movements 

 of the scaphognathites and, later, rhythmic respiratory movements ; the long 

 antennas projecting into the water moved somewhat, the legs and chelae some- 

 times moved and the claws opened and shut. Upon escaping from the spherical 

 egg-case the larva became but little straightened out and remained essentially a 

 spheroidal head-thorax with a weak abdomen bent in under it and with soft, 

 pendent limbs. However, in from one to six hours the limbs reaching about, 

 the claws opening and shutting and the abdomen sometimes flapping up and 

 down, it was seen that the chelae managed to get hold of the stalk of the egg- 

 case. Henceforth the larvae held fast by the chelae though for a time still 

 fastened by the telson thread also. 



The pleopods of the parent were now covered over with a mass of flesh- 

 colored young, showing slight movements and conspicuously marked by the 

 two-lobed, red yolk mass, by the dark eyes and by the yellowish "liver" areas. 

 The dark yolk masses showing through the pale bodies gave somewhat the gen- 

 eral appearance represented in figure 2, which was made from a photograph 

 of a living female shortly after the eggs (excepting one) had hatched. 



When forcibly torn loose from the mother the recently hatched larvae, too 

 spheroidal to rest on their ventral side and unable to stand on their legs, lay 

 for two days on their sides, kicking their legs but unable to walk; when, how- 

 ever, much disturbed, they managed to swim forward along the bottom of the 

 dish by flapping their abdomens, though they still remained on their sides. 

 When offered a piece of rough string, such young seized it and remained sus- 

 pended in the water, holding fast by their chelae. In this way some larvae were 

 kept suspended in running water and successfully carried into later larval 

 stages away from association with the mother. 



This tending to seize hold with the chelae is accompanied by a tendency to 

 push far in amongst the general mass of young attached to the pleopods, so 

 that in a few days all the young are densely crowded together in a compact 

 mass and their long chelae are seen to reach far in and to be fastened either 

 to the stalks of egg-cases or to the coagulum that binds the setae together on 

 the pleopods. Generally both chelae grasped the same egg stalk but not always 

 and one larva was seen holding by one chelae to an egg stalk on one pleopod 

 and by the other chelae to an egg stalk upon the next pleapod. As the rhyth- 

 mic movements of the pleopods continued after the young were hatched, 

 this larva was in danger of having its chelae stretched apart. 



