332 



MORRIS M. WELLS. 



especially the pectorals, which twitched or waved somewhat 

 regularly for several minutes after the opercular movements 

 had ceased. With the final cessation of movement upon the 

 part of the fins, the fish was considered dead. This final cessa- 

 tion of all movement was often preceded in the low oxygen experi- 

 ments, by a sudden violent paroxysm, during w T hich, the fish 

 "scooted" about the bottle in a blindly convulsive manner. 



V. RESISTANCE OF THE FISHES. 



The resistance of the fishes varied with the individual, with 

 the species, and with the size. No reliable data were obtained 

 with regard to individual variation, because of lack of knowledge 

 of the previous history of the animals. Specific and size differ- 

 ences in resistance were however great enough to cover up, to a 

 considerable extent, the unknown individual factor and are to 

 this extent indicatory. With regard to the size (i. e., weight) 

 in the same and different species, it was found that small fishes 

 showed a greater resistance per unit of weight than did the 

 larger ones. At the same time, the larger fishes, because of 

 their excess weight, usually lived longer per individual. These 

 two sets of reactions are clearly shown in the tables which follow. 



TABLE I. 



SHOWING THE COMPARATIVE RESISTANCE OF LARGE AND SMALL FISHES OF THE 



SAME SPECIES TO Low OXYGEN (.i-.is c.c. PER LITER) AND 



MEDIUM CARBON DIOXIDE (15-17 c.c. PER LITER). 



Table I. gives the results of a few typical experiments in 

 which low oxygen (0.1-0.15 c - c - P er !) an d medium carbon dioxide 



