432 SELIG HECHT 



2. According to these results an adult of medium size (ca. 

 100 gm.) moves about 173 liters of sea-water in a day. Large 

 as this quantity seems to be, I am convinced that, if anything, 

 it is less than the normal accomplishment. Ascidia atra is 

 not a good aquarium animal, specimens rarely surviving longer 

 than a few days in the laboratory at the summer temperature. 

 The handling and removal from the water consequent on col- 

 lection and transportation would hardly improve its condition. 

 A case in point is the following experiment. 



Experiment 76, July 30 



12.30 Fixed the tube into the oral siphon. 

 Animal kept out of water 3 minutes. 

 12.45 Average of 10 readings for the time required for carmine parti- 

 cles to travel the length of the glass tube, 3.6 seconds. 

 1.00 Average of 10 readings, etc., 2.4 seconds. 

 3.40 Average of 10 readings, etc., 1.1 seconds. 

 8.25 Average of 10 readings, etc., 0.98 seconds. 

 9.20 Average of 10 readings, etc., 1.3 seconds. 

 10.45 Average of 10 readings, etc., 1.4 seconds. 



Weight of specimen, 69 grams. Visible length of tube, 5.7 cms. 

 Diameter of tube, 0.50 cms. 



It took nearly eight hours for the velocity of the current to 

 reach a maximum, in other words, for the effect of the manipulation 

 at the beginning of the experiment to disappear. I cannot say 

 that recovery was complete, but judging from the appearance and 

 behavior of the animal, I believe that it was nearly so. Recovery 

 therefore is a very slow process. The only experiment which 

 I made with a specimen in its natural environment was unsuccess- 

 ful, and the termination of my stay at Bermuda prevented its 

 repetition. 



3. The above curve shows that the volume of water produced 

 by the current, and hence the total energy of the ciliary mecha- 

 nism in the branchial sac, is not quite a linear function of the 

 weight of the animal. In general the energy manifested per 

 unit weight varies inversely as the size. That this is true for 

 many invertebrates has been maintained by Vernon ('95) and 

 by Flitter ('07, p. 301) and clearly proved for Octopus vulgaris 

 by Polimanti ('13). 



