NEKYOUS SYSTEM OF ASTERIAS. 189 



animal ; from this ring, three delicate filaments are given off opposite to 

 each ray, one of which, according to Tiedemann, runs along the centre of 

 the ambulacra! groove upon the under surface of the body, and gives off 

 minute twigs to the locomotive suckers placed on each side of its course ; 

 the other two filaments pass into the visceral cavity, and are probably 

 distributed to the internal organs. There are no ganglia developed on 

 any part of this nervous apparatus; or if, as some writers assert, 

 ganglionic enlargements are visible at the points whence the radiating 

 nerves are given off, they are so extremely minute as not in any degree 

 to merit the appellation of nervous centres. 



(497.) Such an arrangement can only be looked upon as serving to 

 associate the movements performed by the various parts of the animal ; 

 for no portion of these simple nervous threads can be regarded as being 

 peculiarly the seat of sensation or perception. Nor is this inference 

 merely deducible from an inspection of the anatomical character of the 

 nerves ; it is based upon actual experiment. We have frequently, when 

 examining these animals in a living state (that is when, with their 

 feet fully developed, they were crawling upon the sides of the vessels 

 in which they were confined), cut off with scissors successive portions 

 of the dorsal covering of the body, so as to expose the visceral cavity ; 

 but, so far from the rest of the animal appearing to be conscious of the 

 mutilation, not the slightest evidence of suffering was visible: the 

 suckers placed immediately beneath the injured part were invariably 

 retracted ; but all the rest, even in the same ray, still continued their 

 action, as though perfectly devoid of participation in any suffering 

 caused by the injury inflicted. Such apathy would indeed seem to be 

 a necessary consequence resulting from the deficiency of any central 

 seat of perception whereunto sensations could be communicated. Never- 

 theless Ehrenberg insists upon the existence of eyes in some species of 

 Star-fish, attributing the function of visual organs to certain minute 

 red spots, visible at the extremity of each ray, behind each of which he 

 describes the end of the long nerve that runs along the ambulacral 

 groove as expanding into a minute bulb. We must confess that the 

 proofs adduced in support of such a view of the nature of the spots 

 appear to us to be anytliing but satisfactory. The general sense of 

 touch in the Asteridae is extremely delicate, serving not only to enable 

 them to seize and secure prey, but even to recognize its presence at some 

 little distance, and thus direct these animals to their food. Any person 

 who has been in the habit of fishing with a line in the shallow bays 

 frequented by star-fishes, and observed how frequently a bait is taken 

 and devoured by them, will be disposed to admit this ; yet, to what are 

 we to attribute this power of perceiving external objects ? It would 

 seem most probably due to some modification of the general sensibility 

 of the body, allowing of the perception of impressions, in some degree 

 allied to the sense of smell in higher animals, and related in character 



