432 H. p. KJERSCHOW AGERSBORG 



the same was placed in front of them so as to be touching the 

 Hps. In fact, the animals would then make a swift nip for such 

 foods with the jaws. If an animal, which had not fed for twelve 

 hours, was at rest next to a piece of gonads (the food it ate the 

 most readily) it would immediately become active by being touched 

 on the oral tentacles by the food, and then begin to crawl about. 

 If it came upon the food, feeding started at once. Touching the 

 animal similarly gently on other parts of the body did not result 

 in the active moving about. This may show that the chemo- 

 receptors, as stated above, are better organized or specialized in 

 the oral tentacles. During such forced movements, the animal 

 moved practically in a straight line (in a circle in the finger-bowl), 

 but it bent the head, now and then, from side to side, and was 

 constantly lashing the oral tentacles as if it were feeling its way. 



I repeated Arey's experiment by holding a drop of various 

 kinds of oils between the 'rhinophores' without allowing the oils 

 to come in contact with them, but I did not get any response. 

 Allowing a drop of oil to come onto the body, the oral tentacles 

 only gave definite response. The response w^as — to saffrol, 



and to bergamot oil. The dorsal tentacles, for the same oils 



gave 0. The rest of the body gave — , or 0. The animal 

 does not show any awareness to clove oil when a drop of it is 

 suspended free between the dorsal tentacles. Allowing the same 

 to touch any part of the body the response is — . The response 

 to organnum oil is © for the head and for the rest of the body 

 (vide ut infra tabula). To cedar-wood oil, the response is either 

 or 0. And to orange flavor it is 0. 



The following tables show the exact data relative to the number 

 of specimens used, the size and condition of the specimens, the 

 stimuh employed, the parts stimulated, the relative response, 

 etc., of Hermissenda opalescens Cooper (tables pp. 433-438). 



Arey quotes Crozier as thinking that the dorsal tentacles of 

 Chromodoris are rheotropic, their prime importance being in 

 effecting orientation to the water current. But the dorsal 

 tentacles of Hermissenda do not seem to have a rheotropic func- 

 tion, because specimens with one or both of the dorsal tentacles 

 removed oriented as easily and moved against the current as did 



