1 82 EDWIN B. POWERS. 



was completely anaesthetized but recovered in eight minutes when 

 placed in fresh water. At first it remained motionless in the 

 fresh water but later revived and seemingly became normal. 



2. Ancesthesia and Death. 



An experiment was performed to determine the relative 

 resistance of the four species of crayfishes to high concentration 

 of carbon dioxide. Though the experiment was terminated 

 before the crayfishes had all been killed, through an accident to 

 the apparatus, it had been carried sufficiently far to determine 

 the susceptibility of the four species to the carbon dioxide 

 solution. The apparatus consisted of large glass bottles (Wells, 

 '13) through which water containing from 6.92 to 7 c.c. of oxygen 

 per liter and varying amounts of carbon was flowing. The 

 amount of the gases were determined by titrations of samples of 

 water collected from the over-flow. The temperature was 21.5 

 to 23 C. 



It was found that in all cases the smaller individuals of a 

 species died first. This was probably due to the greater propor- 

 tion of surface to mass in the smaller specimens than in the 

 larger ones, rather than a difference of susceptibility of the 

 smaller specimens to the carbon dioxide solution. These are the 

 same general results obtained by Wells (Wells, /. c.} with fishes. 



All remained active in 50 c.c. carbon dioxide per liter. Virilis 

 was anaesthetized by solutions of 120 to 145 c.c. per liter. Pro- 

 pinquus was not overcome but showed that they were effected, 

 while diogenes and immunis showed the effect to a less extent. 

 Propinquus was not anaesthetized as early as virilis but the time 

 of death approached that of virilis, the small specimens of 

 propinquus having died before the large virilis, but a medium 

 sized propinquus survived all the specimens of virilis. Diogenes 

 and immunis were much less susceptible to the carbon dioxide 

 than either propinquus or virilis. All specimens of both pro- 

 pinquus and virilis died before the medium-sized specimen of 

 diogenes. The specimens of diogenes and immunis died in the 

 following order: One medium-sized diogenes, one immunis, one 

 diogenes, one immunis, two diogenes and two of immunis. There 

 were one immunis and one large diogenes alive when the experi- 



