308 Miscellaneous. 



to move towards its invisible prey ; then, on arriving at the division 

 which separates it from the bait, it attempts to thrust one of its 

 arms beneath the obstacle. Thereupon T raise the board a little ; 

 the Starfish at once takes advantage of this ; with much labour it 

 stretches its arm beneath the board and seizes the fish placed on the 

 other side. 



It thus becomes evident that the very rudimentary organ of vision 

 does not help the Asterias in seeking its food, and that the sense of 

 smell alone serves as its guide. 



e. Into a tub containing a stationary Asterias we let fall, without 

 disturbing the water, a few drops of sea-water in which a fragment 

 of fish has been crushed ; the Asterias manifests the same excite- 

 ment and goes through the same movements as if the fish itself had 

 been presented to it. 



(3) /. I cut off the four distal ossicles of the five arms of an 

 Asterias, so as to deprive the animal of all its palps. To-day more 

 than a month has elapsed since the operation, and I have never been 

 able to obtain from this Asterias the slightest show of excitement on 

 presenting to it a bait either dead or alive, although before being 

 operated upon the animal was very active in seeking its prey. 



g. I removed all the palps of an Asterias, leaving the eye-spots. 

 This animal, which in a trial experiment had been quick enough in 

 seizing a linen bag containing a morsel of fish, no longer exhibits 

 excitement on the approach of a bait ; and when food is placed in 

 the tub in which it lives with other specimens of Asterias glacialis, 

 it alone remains absolutely motionless. 



These experiments prove that in Starfish the sense of smell is not 

 diffused, but is localized in the ambulacral tentacles unfitted for 

 locomotion, situated behind the eye-spot. 



h. We divide the ambulacral nerves of the five arms of an Asterias 

 at about 2 centimetres from the tip, so as to isolate in each arm a 

 distal portion carrying not only the palps, but also a small number 

 of ambulacral tentacles. When a bait is offered to this Asterias its 

 palps are at once erected, and the stimulus is rapidly transmitted to 

 the ambulacral tentacles of the distal extremities, but stops abruptly 

 opposite the point where the nerve was divided. The result is that 

 while the tips of the arms, which are powerfully excited, endeavour 

 to set the Asterias in motion, the rest of the body, not receiving the 

 sensations experienced by the tactile organs, remains absolutely 

 impassive. This state of things had been foreseen, since we had 

 severed the principal channel of nervous communication between 

 the palps, alone capable of appreciating odours, and the great 

 majority of the motile organs of the Asterias. I say the principal 

 channel, for the superficial nerve-plexus has also to be reckoned 

 with. We must conclude, however, that it plays a very subordinate 

 part in the transmission of odours, since 1 only once saw the Asterias 

 which had been operated upon set itself in motion after having been 

 solicited by its extremities for a quarter of an hour ; and even then 

 it did not travel towards the bait. — Archives de Zoologie crpirimen- 

 tale ft generate, ser. 2, t. viii., Annee 1890, no. 4, pp. xxxvi-xxxviii 

 (Cowpte* Bendus, ex. (1890), pp. 1343-1346). 



