36 



HAROLD SAXTON BURR 



larvae resulted in not a single positive reaction, the individuals 

 would invariably swim off without paying any attention to the 

 Daphnid, or after a time the entomostracan would move away. 

 The above experiments were performed on larvae varying from 

 one and a half to four months old, dating from the time of oper- 

 ation, and indicate that these larvae do make use of the sense 

 of smell in obtaining their food. This was further corroborated 

 by the following tests on the eyeless forms (table 2). 



The eight eyeless larvae were subjected to the same tests. 

 Out of one hundred and twenty-nine, one hundred and nineteen 

 were positive, giving a percentage of ninety-two, a very close 

 correspondence with the normal. Here the olfactory sense was 

 the only one held in common by the normal and eyeless larvae 

 that could receive stimulation. 



A curious phenomenon, to be investigated later, was observed 

 in connection with the eyeless individuals. They were very 

 much more sensitive to currents in the water than the normal 

 larvae. A pipette waved in the vicinity of the tail of the eyeless 

 larvae would cause it to turn sharply around and snap at the 

 pipette. No such extreme sensitiveness was observed in the 

 normal larvae. The latter would snap at a pipette but only 

 when waved with the characteristic jerky movement of its normal 

 food. It is suggested that this peculiar action of the eyeless 

 larvae is due to a compensatory hypersensitiveness of the lateral 

 line and general cutaneous systems. 



In the spring of 1914, one year after the above experiments 

 were performed, a number of larvae, probably A. opacum, were 

 brought into the laboratory from the field. These were about 

 30 mm. long — evidently developed from eggs laid the previous 



