56 University of California Publications in Zoology [Vol.19 



the net so that the animals passed into a larger amount of water than 

 when a bottle was used. But perfectly satisfactory material has been 

 obtained in the latter case, and very poor in the former. Water from 

 the laboratory supply, as contrasted with that carried in from the pier, 

 is not always to be blamed. One animal lived for three days in sea 

 water drawn from the pipes, without changing the water, and the 

 specimen was apparently in as good condition on the third day as on 

 the first. Its death was due to exposure to direct sunlight. If the 

 animals are in good condition handling them does not have an un- 

 favorable effect. It is necessary to pick them up with a pipette, and 

 this must be done carefully of course, but it does not interfere with 

 their activities. Pouring from one dish to another is not injurious. 



On the whole, I do not know of anything that will insure one's 

 having good material. It must be taken as it comes. Specimens can 

 practically always be obtained but their condition is problematical. 

 With identical treatment they may at one time be perfectly satisfac- 

 tory and at another be the opposite. 



Sagitta is not a particularly rapid swimmer, even when disturbed, 

 as by the approach of the pipette. The animals are expert "dodgers," 

 and this combined with the transparency of the body makes it difficult 

 to catch them. Swimming is accomplished by making strokes with or 

 by "flirting" the tail. At each stroke the animal moves forward a 

 short distance, and this action is kept up continually. The animals 

 can even swim backward by what is to all appearances the same 

 method of propulsion as that used for locomotion in the opposite 

 direction. 



Another difficulty met with in using Sagitta is that of seeing the 

 animals, particularly in a large dish of water. It is not hard to keep 

 track of an individual nor to count a number of animals in a tube 

 when one can look through the water toward the light. I found it 

 impossible to do anything, however, by looking down into a dish of 

 water from above. 



I believe that there need be no hesitation in using animals that 

 have been in the laboratory, so long as they are swimming about ; that 

 is the best test of condition I have found. I did not reject specimens 

 even on the second day, and I think that their reactions then are as 

 characteristic of the species as those of any animals in the laboratory. 



