316 EDWARD C. DAY 



general sensitiveness and, 2) a complete break in the coordination 

 of the siphons. While each siphon was capable of responding 

 when stimulated directly, it did not join in the response when 

 the other siphon was stimulated, as was the case before the 

 operation. This state of incoordination lasted until the gan- 

 ghonic tissue regenerated, about four to five weeks later. 



A brief history of a single case will illustrate the course of events 

 following an operation on the ganglion. 



Protocol 4- Ascidia mentula no. 2. April 12. Animal removed 

 from water and ganglion extirpated. Oral siphon opened immediately 

 after operation and before animal was returned to the water; aboral 

 siphon remained closed. 



April 15. Siphons both responsive to tactile stimulation with a 

 bristle and to tapping on table or jar with a scalpel. No coordination 

 between the two. The tentacles are also sensitive to penciling, and 

 when they are touched the oral siphon closes. 



April 26. Siphons both responsive to stimulation. No coordination. 



May 5. Faint signs of recoordination between the siphons. 



May 9. Coordination of siphons definitely reestablished. Out of 

 ten trials in which the oral siphon was stimulated with a camel's-hair 

 brush, the oral siphon responded ten times and the aboral seven, the 

 sequence of contraction being from oral to aboral with a latent period 

 of about one-half second between the two responses. When the 

 aboral was stimulated, out of ten trials the oral siphon responded five 

 times to its ten, the sequence being aboral to oral. The regenerated 

 ganglion can be recognized as a small whitish body lying in the region 

 of the original one. 



The other three animals which had been operated upon at the 

 same time as the one whose history has been given above, had 

 also regenerated their ganglia, and, upon being tested, showed 

 that the coordination of the siphons had likewise been re- 

 established. The fifth ascidian, whose ganglion had been de- 

 stroyed with nitric acid, died a week after the operation. Up to 

 that time, however, the siphons retained their independent 

 sensitivity, but no coordination existed between them. 



Two weeks earlier, but three weeks after the removal of the 

 ganglia, none of the four ascidians exhibited any signs of co- 

 ordination, although the siphons responded independently to 

 direct stimulation. At the end of five weeks, however, the 

 stimulation of one siphon brought about not only the closure of 



