E. W. BERGER ON THE CUBOMEDUS^E. 25 



Walking with the jar about the laboratory did not suffice to 

 make any change in their swimming, nor did blowing on the surface 

 make any appreciable change. 



b. Upon taking the jar to the back porch and placing it on the 

 stone or cement flags, in the shade and a cool breeze, in four 

 minutes time all were on the bottom not even pulsating. 



Upon replacing them on the laboratory table all began to swim 

 about at once. [Repeated.] 



c. The jar (1) was placed on the back porch again ; in fifteen 

 seconds three were on the bottom ; in one-half minute all but one. 

 In three or four minutes all were on the bottom, but two were 

 swimming lively and the others pulsating. In another minute all 

 were swimming. 



d. The jar (1) was tried again, not resting it on the flags but 

 holding it by my hands on the -sides. The effect was just as quick; 

 they stopped pulsating at once. By the time I had got back to my 

 table in the laboratory, one was at the surface and another arrived 

 just as the jar was set down. 



[Several other experiments of an order similar to those just noted 

 were tried, with very similar results.] 



5. Two buckets stood side by side in the laboratory. One bucket 

 (1) had more Charybdeas in it than the other bucket (2), and also 

 had more since brought in (about an hour). The water of one (1) 

 was also more discolored and with more organic matter (sea weed, 

 etc.). In the laboratory the animals were active on the surface of 

 both buckets. Placed in the sunlight on the porch, no breeze, the 

 sun slanting so that one side of the water in the buckets was 

 bright while the other side was shaded, the jelly-fish in (1) went 

 mostly to the bottom, while those in (2) seemed unaffected though 

 some showed a tendency to go to the bottom after a longer 

 exposure. The experiment with (1) was repeated and it took some 

 five minutes for them all to go to the bottom. In a few minutes 

 after replacing them in the laboratory several were active again on 

 the surface. 



6. Jar (a) with five large ones stood on my table ; they were quite 

 active. Placed in the sun (no breeze), on the porch, one or two sank 

 to the bottom at once and the others seemed to slow their activities 

 somewhat but not very markedly. In a few minutes all were swim- 

 ming, apparently more actively than before, in the bright sunlight. 



3 



