322 EDWARD C. DAY 



SENSORY RESPONSES OF ASCIDIA ATRA LESUEUR 



Since my experiments on Ascidia atra were of a preliminary 

 character, there are only a few which may be mentioned here. 

 For a good account of the physiology of this species reference 

 should be made to the research of Hecht ('18). The response to 

 various forms of stimulation are briefly as follows: 



Tactile stimulation. When the outer surface of the test was 

 stimulated with a bristle, the base and column of the animal 

 were found to be insensitive, the necks of the siphons moderately 

 sensitive, and the margins of the aperatures most sensitive of 

 all. According to the strength of stimulation, the siphons 

 respond independently or coordinately. 



Vibratory stimulation. Tapping on the jar or, when the 

 animals are in their normal habitat, stamping on the sand or 

 clapping two stones together under water causes the siphons to 

 close. 



Chemical responses. Acetic acid 1, 0.1, and 0.01 per cent 

 strength when pipetted on the incurrent siphon caused it to 

 close, but had no effect on the excurrent. A weaker solution 

 of the acid, 0.001 per cent, and distilled water were both without 

 effect. 



An animal put in one-half per cent solution of ether in sea- 

 water became totally narcotized in eight minutes. It bent over 

 double on itself during the process, closed its siphons, and 

 became quite insensitive to tactile stimulation. When returned 

 to running sea-water again, it revived in twenty to twenty-five 

 minutes; the animal straightened somewhat, both siphons opened 

 and responded to stimulation with a bristle. 



Either siphon could be locally anesthetized by pipetting a 1 

 per cent solution of chloroform in sea-water on to it. With 

 both siphons rendered insensitive in this way, the animal still 

 exhibited the ciliary current entering the oral and issuing from 

 the aboral siphon, and it also gave vomiting reactions from time 

 to time, forcibly ejecting water from both siphons and thereby 

 indicating that the body musculature was still active. 



