384 Uiiiversiiij of California Publications in Zoology [Vol. 16 



also something that must be known if habits are to be accounted for 

 on the basis of reactions. 



The animals were always taken in an open plankton net, with a 

 wide-mouthed four-ounce bottle tied into the peak of the net. Thus 

 they were never out of water and were not subjected to rough treat- 

 ment. Collecting was done at the end of the pier (about 1000 feet 

 from shore) or further out, in deeper water, from a boat. In the 

 laboratory- the animals were kept in finger-bowls. No attempt was 

 made to furnish running water, but that in the stock vessels was 

 changed at intervals. The animals used in experiment were handled 

 by means of a wide-mouthed pipette and they were never forcibly 

 drawn into or expelled from the tube. Mechanical stimulation of any 

 sort was avoided in all possible waj^s. The lighting conditions in the 

 general laboratorj^ are those of ordinary diffuse light, chiefly from 

 the north. The animals were never in direct sunlight. 



All of the tests here referred to consisted in releasing single 

 animals at the center of a circle 16 cm. in diameter, in a shallow 

 dish. The nature of the response and the time taken to travel 8 cm. 

 were noted at the circumference of the circle. The work on reactions 

 was done in a room with black walls to which north light could be 

 admitted through a window 50 by 40 cm. The inside of the wall of 

 the dish was covered on the half awaj' from the light with a mixture 

 of lampblack and paraffine, and reflections from other .sources were 

 cut off as far as practicable by black screens. In the tables that 

 follow the number of animals is not set down, but on the average 

 there are about half as many animals as trials. Only adult males 

 or females were used. 



Table 1 summarizes the results obtained with females of the two 

 species that came //( the same hauls at the surface. 



TABLE 1 



Female.s op Ac.\etia tonsa and a. clausi tkom the Surface 



Comparison of responses of the two species to light from window 1 metre away ; 

 tUstance and time taken from center to circumference of 16-cm. circle. The 

 effect of low temperature is shown. 



No. of Per cent of Av. time Av. no. 



liours 

 after 

 Temp. capture 



1. Tonsa Over 15° C li/o-S? 



2. Clausi Over 15° C IVo-S? 



3. Tonsa 15° Cor less Vo-T 



4. Clausi 15° C or less y2-7 



Note. — The sum of the numbers in the fourth and fifth columns, fourth line, 

 does not equal the total, because in some trials the animals did not cross the 

 circle. 



