MARINE ANIMALS. 73 



kind the plates being so closely placed^ and so hard that there is, in fact on the* 

 upper part, no means by which spines could protrude themselves; their presence 

 will be detected around the mouth on the lower or concave portion, as if the 

 denial of egress on one portion was made up by its production on another. 



These spines when living, (if I may use the expression,) are discovered to 

 be coated by a secreting membrane, which is the agent of their growth, and 

 not only do they thus grow, but it has been found that where a spine was 

 bitten off by some fish of prey, probably, having seized, but failed to swallow 

 the Echinus itself, the imperfect end was reproduced, and in some specimens 

 a longitudinal section will shew the point at which such repair took place; 

 and in others not only once but twice in the same spine. Being quite isolated 

 from the body as they are, it was not until the external secreting membrane 

 was discovered that the source of their growth was known; but being so 

 known, sections of them shew distinctly the layers of increase, in the same 

 manner as trees exhibit their rings of woody fibre. In most of the Echinis, 

 each of the five ground divisions of the shell is grooved, and furnished with 

 a row of tubercles; both being regulated in graduation of size by the shape . 

 of the shell itself, and thus are formed ten rows of anibulacral plates, between 

 which tubular suckers or retractile feet are protruded at will; and these 

 feet are of course regulated by and connected with the animal's internal 

 economy. 



That the Echinus becomes the prey of other marine animals, is established 

 by the fact that great numbers have been found in the stomachs of fishes; 

 but whilst we record this, it must not be forgotten that they themselves 

 are furnished with a most complicated and curious feeding apparatus, in which, 

 in my present paper, I can only notice that the number five is observed, as 

 in the shell, in a remarkable manner. The plates around the mouth are 

 moveable, and within them there are five teeth, which work upon five jaws, 

 provided with five processes, and attached to five long and slender levers; and 

 thus the number five, as I have before observed, is remarkably carried out; 

 and this Pentenumeral apparatus forming the mouth, was thought by Aristotle 

 to resemble a lantern, and is still known by that name. 



As my space will not now allow me to enter into details upon this most 

 singular division of Marine Animals, I shall only further observe that the 

 Echinus, to which I have devoted this paper, is only one of its types; and 

 therefore without observing the strict order pursued by naturalists, I shall 

 take each in its turn as it occurs to me, at the same time not so wholly 

 discarding all method as to be silent on the actual place which science has 

 assigned them amongst the inhabitants of the ocean. 



Inert and helpless as these ball-shaped beings naturally appear, every one 

 of the spines which protrudes from them, arises from a tubercle having a 

 socket, and capable of motion in every direction; and the suckers to which 

 I have before alluded, aided by these spines, which are in fact so many 

 hundred, or, in some cases, thousand, legs, enable the animal to transport 



VOL. II. L 



