MARIAN IRWIN 213 



celeration being about three times the normal; in both cases de- 

 crease takes place after the increase. The reason the initial decrease 

 is less with 7.3 per cent ether than it is with 3.65 per cent, is that the 

 acceleration takes place more rapidly in case of the former, thus pre- 

 venting the further decrease in CO2 output. 



Both 3.65 and 7.3 per cent ether caused peeling of the cuticular layers 

 of the epidermis; this reaches a maximum in 20 minutes in 3.65 per cent 

 ether, and in 5.5 minutes in 7.3 percent ether. During the first 4 min- 

 utes in 3.65 per cent ether no peeling was observed. It might be sup- 

 posed that this peeling causes an apparent increase in CO2 production 

 by allowing the CO2 to escape more freely. However, the extent of 

 the peeling seems to be the same in both the 3.65 and the 7.3 per cent 

 solutions, although the acceleration in the CO2 output in the former 

 concentration is much greater than the latter. This difference can- 

 not therefore be wholly due to the peeling of the skin. 



Both the breathing movements and the body movements cease at 

 these concentrations in less than 10 seconds after immersion of the 

 tadpoles in the solutions. This might be thought to account for the 

 drop in the rate of CO2 output, but in view of the fact that we find a 

 similar drop in Fig. 1, where the movement remained normal, we are 

 obliged to conclude that the cessation of the muscular movement can- 

 not account entirely for the falhng off in the CO2 output. This con- 

 clusion is confirmed by the experiments on frog eggs. 



Aquatic Insects. 



In order to avoid the disturbances due to the peehng of the epi- 

 dermis, an aquatic insect was chosen. This is the common whirhgig 

 beetle, Dineutes assimilis Aube. It possesses a chitinous covering 

 which prevents any peeling. 7.3 per cent ether solutions were used. 

 Fig. 3, Curve A, shows a 94 per cent decrease in CO2 output, after 

 which an increase takes place followed again by a decrease. 



The activity of these insects is much greater than that of tad- 

 poles and a correspondingly greater drop in CO2 output is to be 

 expected as the result of anesthesia. 



