OCEAN LIFE, 35 



spines, be they as thin and delicate as th<; fine pile of velvet, 

 such as exist in the Clypeaster and in other flattened genera, or 

 large and club-shaped, as in Cidarites, the joint is equally com- 

 plete and movable in all required directions. In the last men- 

 tioned race, indeed, we see additional provisions made to give 

 secure attachment, the centre of each tubercle being furnished 

 with a little pit, from which arises a strong ligament that is im- 

 planted in the base of the appended spine to obviate all chance 

 of dislocation. 



" To understand the mode in which the spines are all produced, 

 and fixed upon the body of the Echinus, we must again refer to 

 the soft tegument whereby the numerous pieces of the shell are 

 all secreted. The skin, which is, in fact, the living substance 

 of the creature's body, likewise constructs the spines, and if a 

 section of one of th'ese is prepared, taken from a recent speci- 

 men, each will be found, encrusted over with a layer of this soft 

 fleshy membrane, as were the stems of corals, or Crorgonice ; and 

 in like manner, the investing film is able to secrete cretaceous 

 particles, which are arranged, stratum investing stratum, with 

 such art and regularity, that few more beauteous objects can be 

 found, than one of these neglected spines." 



" The suckers of the Echini, in all essential particulars, re- 

 semble exactly those of an Asterias, consisting of long projecti- 

 ble fleshy cylinders, which are protruded and rendered tense 

 by water, or some other fluid injected into them, from an appara- 

 tus contained within the body. The degree to which the protu- 

 sible tube can be exerted will of course differ in every genus in 

 proportion to the length of the locomotive spines, it being abso- 

 lutely necessary, that, however long the latter organs may be, 

 the prehensile portion of the sucker shall be able to reach be- 

 yond them ; so that in the long spined genera, of which, in warm 

 climates, some are found having spines several inches in length, 

 the tubes, with their appended adhesive discs, resemble little 

 cables thrown out to a distance, for the animals, in order to secure 

 an anchorage, or ropes whereby to hoist themselves from ledge 

 to ledge, of the steep rock, on which their food is found. 



" These suckers that surround the mouth perform, besides, 



