SEVENTH ANNUAL MEETING S3 



and proportionately with the change in temperature, but at 

 the higher and lower limits of temperature used in these ex- 

 periments, there is a breaking over the bounds of normal ac- 

 tivity and a period of abnormal activity ensues. This period 

 has been described in the case of high temperatures, where it 

 comes on as the temperature nears the death point for the 

 species, and it will occur whether the heating be slow or rapid, 

 the only difference being that with slow heating, it occurs at 

 a higher temperature than when the heating is rapid (.5°-1.5° 

 C. difference for the different rates tried). In the experiments 

 where the fishes were changed from warmer to colder water it 

 was found that with certain changes a paroxysm of activity 

 similar to that of heating follows the transfer. To produce 

 this result the temperature change must be sudden and rela- 

 tively great. With Notropis blennius adults, for instance, a 

 sudden change into water which is at least 10° C. colder than 

 that in which the fish has been kept will produce upon the part 

 of the fish violent activities, providing the lower temperature is 

 not above 5°-6° C. Thus a sudden change from 15° C. to 3° C. 

 will give the reaction, while a change from 25° C. to 13° C. 

 will merely result in a decrease of normal movements, as rate 

 of gill contractions, etc. A gradual cooling of the surround- 

 ing water does not result in any marked reaction at any point 

 down to freezing (Heath '83). A typical experiment will 

 illustrate this reaction in which the paroxysm, due to change 

 from warmer to colder temperature occurs. "An adult No- 

 tropis blennius was suddenly transferred from water whose 

 temperature was 13° C. to water of 3° C. The fish had been 

 kept in the 13° water for four days. When dropped into the 

 cold water, it lost all motion and gill movements could scarce- 

 ly be detected. It lay thus on its side for 1 minute and 30 

 seconds; began to swim a little, and then suddenly "scooted" 

 madly about the pan. This blindly violent activity lasted for 5 

 seconds ; fish again fell to side ; lay motionless for 5 seconds ; 

 pectoral fins began to twitch ; gill movements weak and irregu- 

 lar; gradually movements of gills and fins became more vigor- 

 ous until at end of 22 minutes, fish was swimming about pan ; 

 still unable to maintain equilibrium ; at end of 34 minutes 

 floating easily and normally in the cold water." The bull-head 

 does not show any such marked reaction, however great the 

 temperature change, its adjustment remaining within the 

 bounds of normality in all changes from warmer to colder 

 water. Small cyprinid fishes were less affected by the change 

 from warm to cold than were adults of the same species, 

 the small fishes as a usual thing not passing through a par- 



