No. 4-] AMPHITHOE LONG/MAX. I SMITH. \ Sy 



forms of amphipod behavior could be traced, it would be found, 

 I believe, that thigmotaxis is the mother of many instincts. 



The Instincts of tlic Young. 



When the young of Amphithoe quit the maternal brood 

 pouch, they have a quite different appearance from the adult. 

 They are whitish in color, with only a very few pigment spots, 

 located for the most part on the epimera, each epimeron con- 

 taining often but one spot. These pigment cells are of a 

 greenish-gray color and apparently have none of the reddish- 

 brown pigment which is found in those of the adult. By 

 reflected light they have a light greenish-silvery appearance 

 much like the large light green cells of the adult, but they 

 are very much smaller and much less branched. The head is 

 relatively large, but the eyes are small and red and composed 

 of only six ocelli, one of which is in the center surrounded by 

 five others. The number of ocelli, therefore, increases very 

 greatly as the animal grows older. Both pairs of antennae are 

 short, the flagella of the first pair consisting of four joints and 

 those of the second pair of but three. 



The young when first hatched are in a feeble condition and 

 are carried about for a few days in the brood chamber of the 

 mother. Before they are hatched one can easily see the beating 

 of the heart and the peristaltic movements of the intestine. 

 Shortly before their emergence the young may be observed 

 flexing and extending the body in the effort to break the shell. 

 In one case I removed a lot of eggs from the brood pouch of 

 the mother while they were hatching. Those that had not yet 

 emerged were very vigorous in their movements within the 

 shell. When hatched they were unable to swim, and their 

 movements were irregular and little coordinated. The next 

 clay a few had died ; the others could swim feebly, but none 

 well, and if they became caught in the film at the surface of 

 the water they were unable to overcome the surface tension 

 and get free. In another case I removed from the brood 

 pouch of a female several young that had been hatched only 

 for a short time, as they were feeble and scarcely able to swim. 



