NERVOUS SYSTEM OF THE TUNICATE 



331 



Stimmary of tables 2 and 3 



A, TOTAL REACTIONS 



For 15-mm.2 beam 



For 5-mm.^ beam 



Summary for both 



B. Average time of response: 



For lo-mm.2 beam 



For 5-mm.- beam 



INCURR. SIPHON 



5 out of 35 

 trials. 



1 out of 35 

 trials. 



6 out of 70 

 trials. 



GANGLIONIC 

 REGION 



30 out of 32 

 trials. 



26 out of 33 

 trials. 



58 out of 65 

 trials. 



4.2 sec. 

 8.9 sec. 



EXCURR. SIPHON 



3 out of 6 

 trials. 



out of 35 

 trials. 



3 out of 41 

 trials. 



1 out of 35 

 trials. . 



1 out of 35 

 trials. 



was obtained before the lapse of twenty seconds, the reaction 

 was counted as negative and recorded as 20^-0, as in trial 1, 

 table 1, but if a contraction occurred, as in trial 4, at the end 

 of twelve seconds, it was recorded 12"- + , indicating a positive 

 response. In table 3 ten seconds w^as the time limit allowed 

 for the response. 



It will be seen from table 1 that the body of the animal gave 

 no response out of the five times tested, the ganglionic region 

 but 1 out of 25, the incurrent siphon 4 out of 25 and the ex- 

 current 5 out of 25. Since all the animals were exceedingly 

 sensitive to stimulation by tapping on the jar, the small number 

 of responses here obtained indicate little if any sensitivity to light. 



Table 2 indicates, in contrast to the results obtained for 

 Ascidia m., that the ganglionic area of Ciona is decidedly sensi- 

 tive to light, yielding 32 responses out of 32 stimulations, while 

 the siphons and body are relatively insensitive. The body 

 responded but once in 35 trials, the incurrent siphon 5 in 35, 

 and the excurrent 3 times in 6 trials. Since the excurrent siphon 

 is much shorter than the incurrent, the 15-mm.- beam could 

 not be focused upon it without its overlapping the ganglionic 

 region somewhat, it was therefore not tested as frequently as 

 the other parts, but left for a more critical test with a smaller 

 beam. 



