1917] Estcrly: Specif city in Behavior 385 



The table gives reasonable ground for the following conclusions: 

 (1) Both species are always positive to daylight if the temperature 

 is above 15° C. (2) At lower temperatures, most individuals of tonsa 

 are positive, while most of clausi are negative. (3) Laboratory 

 conditions do not have any ascertainable effects at the higher tem- 

 peratures. (4) The locomotion of clausi is always slower tlian that 

 of tonsa. 



The second item reveals the most striking difference between the 

 two species. I have made several different tests of sets of tonsa and 

 clausi from the same hauls, first at temperatures of 11° C to 13° C, 

 and then with the same animals at 19°-21° C. In tlie cold water 

 clausi is practically always negative and tonsa practically always 

 positive. In the warmer water both are always positive. These 

 results are incorporated in table 1, but the conditions just mentioned 

 do not appear. 



It is worth emphasizing that here are two species of one genus, 

 neither of which is made positive by cooling, while both become posi- 

 tive by warming. On the contrary, cooling has the effect of causing 

 negative responses in representatives of both the species, but to a 

 greater extent in clausi. One of the generalizations given by Loeb 

 (for example, 1913, p. 480) is tliat cooling induces positive helio- 

 tropism which is displaced by raising the temperature ; yet our com- 

 monest forms do not come under this general rule. This lack of 

 conformity between the results obtained from many forms studied 

 by Loeb and the results so evident here should make plain the need 

 of ascertaining the differences between species before drawing general 

 conclusions. 



2. Effect of LAnoEATORY Conditions 

 I believe that this effect must be considered in anj- study of behavior 

 the object of which is to furnish the explanations of habits in nature. 

 If the experimenter wishes only to study the general physiology of 

 any organisms, it is well to "accustom them" to laboratory conditions, 

 for in that way he will get rid of some troublesome variations. It 

 is necessary, however, if one works with the former end in view, 

 first to determine whether animals just taken from their natural 

 surroundings react as they do several hours later. 



For example, specimens of tousa that have come from the surface 

 are apparently not affected by the change from the sea to the labora- 

 tory. In 126 trials, that do not enter into table 1, made after the 

 animals had been in the laboratory from twelve to eighteen hours, all 



