2/0 A. S. PEARSE. 



quence is shown in the use of the tentacles. Number 7 was used 

 eight times ; numbers i, 2, 3, 8, seven times ; numbers 4 and 10, 

 six ; and number 9, five times. The time required for the fifty- 

 three reactions was nine minutes and thirty seconds. A little 

 over ten seconds was therefore required for the wiping of each 

 tentacle. No account was taken of the two ventral tentacles in 

 this series as they kept moving in and out almost constantly and 

 without any apparent relation to movements of the others. In 

 another larger series the different tentacles were used the follow- 

 ing number of times : No. i, twenty-one ; No. 2, sixteen ; No. 3, 

 fourteen ; No. 4, twelve ; No. 7, eleven ; No. 8, fourteen ; No. 

 9, twenty-one; No. 10, nineteen. In this case tentacles i, 

 10 and 9 were nearest the surface of the sand and they were 

 used most frequently while those on the opposite side of the 

 mouth (3, 4, 7) were less often employed. The time for this 

 series of one hundred and twenty- eight reactions was fifteen min- 

 utes and thirty seconds, seven and a quarter seconds being re- 

 quired for the wiping of each tentacle. 



The feeding reaction usually occurred only after an individual 

 had been undisturbed for some time and when it was partly 

 buried in the mud or sand, but animals were sometimes observed 

 to feed when attached to the side of a jar. No stimulus was 

 found which would cause Thyone to extend the tentacles and 

 feed. Attempts were made to induce animals to perform the 

 feeding reaction by allowing crab or fish extract to flow gently 

 over the anterior end ; and by using mud from the place where 

 they were collected, but such stimuli were without results or 

 caused only the withdrawing reaction. In one instance, how- 

 ever, a positive reaction was observed. In this case a small por- 

 tion of a bryozoan colony {Bugidd) was dropped in such a way 

 that it fell upon the anterior end of a partly buried individual. 

 The tentacles were at once extended and the anterior end of the 

 body was bent over so that they scraped the point where the 

 stimulation had occurred. This experiment was repeated many 

 times and on different individuals but no other positive reaction 

 was induced. From these observations it may be concluded that 

 the feeding reaction occurs only after the animal has been undis- 

 turbed for a time and is probably brought about mostly by inter- 

 nal factors, such as hunger. 



