ECHINODERMATA. 159 



ments 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 at least, if, as some writers assert, 

 ganglionic enlargements are visible at the points whence the ra- 

 diating nerves are given off, they are so extremely minute as not 

 in any degree to merit the appellation of nervous centres. 



(200.) 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 re- 

 garded as being peculiarly the seat of sensation or perception. 

 But this inference is not 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 scissars 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 inva- 

 riably 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 in- 

 deed seem to be a necessary consequence resulting from the defi- 

 ciency of any central seat of perception, whereunto sensations could 

 be communicated ; nevertheless Ehrenberg insists upon the exist- 

 ence of eyes in some species of star-fish, attributing the function of 

 visual organs to some minute red spots visible at the extremity of 

 each ray, behind each of which he describes the end of the long 

 nerve which runs along the ambulacral groove as expanding into a 

 minute bulb. We must however confess, that the proofs adduced 

 in support of such a view of the nature of these spots, appear to us 

 to be anything but satisfactory; and as we have already stated in 

 the first chapter the physiological objections which may be urged 

 against the possibility of any localised organ of sense being co- 

 existent with a strictly nematoneurose condition of the nervous sys- 

 tem, they need not be repeated here. The general sense of touch in 

 the Asteridse is extremely delicate, serving not only to enable them 

 to seize and secure prey, but even to recognise 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 



