30 University of California Publications in Zoology [Vol.19 



On the whole, the fact that the animals become positive in water of 

 low temperature is clear and unmistakable. 



If the salinity is increased while the temperature remains that of 

 the room (second line of table 4) there is no significant change in the 

 behavior as compared with that at ordinary temperature and salinity 

 (line 1). The animals are clearly negative to light under both condi- 

 tions, and it does not appear that there is positive phototropism to an 

 increased extent when the concentration of the water increases. As 

 a matter of fact it is shown in line 4 that at high salinities and low 



TABLE 5 



The Changing Distribution of Six Specimens of Calanus in a Dish Divided into 



Five Sectons, as the Temperature Decreased Slowly and then Increased 



Salinity 33 to 34 o/ 00 . 



Note. — From 1:50 to 2:35 the animals were exposed to the light from three 

 north windows; for the rest of the time to the light from the 100-watt lamp 

 without the "daylite'' filter through an opening 10 cm. square, the center of 

 the coil being 14 cm. from the wall of the aquarium; this intensity is about 

 200 times that of the 15-watt lamp. 



temperatures there is less positive and more negative phototropism 

 than when the temperature is low and the salinity normal. It is 

 difficult to say, however, how much significance there is in the results 

 given in the last line of table 4, but it would seem that the high salinity 

 counteracts to some extent the effect of the low temperatures. Loeb 

 (1893, p. 98) states that increase of concentration increases the posi- 

 tivity of copepods and also of Polygordius larvae (p. 94). Ewald 

 obtained similar results with Balanus larvae (1912, p. 606). It is 

 certain that Calanus does not become increasingly positive in water 

 of high salinity. 



