54 



ECHINODERMS. 



to this mode of progression, for, impossible as it might seem from their out- 

 ward appearance, they are able to climb rocks in search of food, and thus 

 obtain the Corallines and substances upon which they principally feed. To 

 enable them to effect this, their shell is perforated with ten rows of small 

 orifices, extending from one pole to the other, like the lines of longitude upon 

 a globe, through which long suckers issue similar in structure to those of the 

 star-fish, but long enough to extend beyond the points of the spines ; so that, 

 by their assistance, the sea-urchin not only scales the cliff, but creeps along 

 pendent from the roofs of submarine caverns. 



The number of these suckers is very great : in a moderate-sized urchin 

 Professor Forbes reckoned sixty-two rows of pores in each of the ten bands ; 

 as there are three pairs of pores in each row, their number multiplied by six 

 and again by ten would give three thousand seven 

 hundred and twenty pores; but as each sucker occu- 

 pies a pair of pores, the number of suckers would be 

 half that amount, or one thousand eight hundred 

 and sixty. Nor is the structure of these animals 

 less complicated in other respects. The shell is 

 made up of above three hundred pieces of one kind, 

 and nearly as many of another, all dovetailing toge- 

 ther with the greatest order and regularity, bear- 

 ing on their surfaces above four thousand spines ; 

 nay, if we cut any individual spine into slices and 

 examine it with a microscope, it will be seen to pre- 

 sent a pattern peculiar to the species, and far beyond 

 the reach of art in its elaborate beauty (Fig. 49). 

 Truly the skill of the Great Architect of Nature is 

 not less displayed in the construction of a sea- 

 urchin than in the creation of a world ! 



The eggs (or roe) of the Echinus are looked upon 

 in some countries as affording a very excellent dish, 

 FIG. 49. SPINE OF ECHINUS, and we find that among the Romans they were ac- 

 Segment of section. counted delicacies. It is recorded that they formed 



the principal dish at the famous supper of Lentulus, 



when he was made Flamen Martialis, or Priest of Mars ; and sea-urchins are 

 still caught in great numbers upon the shores of the Mediterranean for the 

 sake of their roe. 



The Sea-Cucumbers (Holotkuria)* (Fig. 50). The fisherman's dredge 

 occasionally brings up, on our own coasts, slimy creatures, bearing no slight 

 resemblance to a disagreeable-looking cucumber, whence they are commonly 

 known by the name of Sea- Gherkins or Sea-Cucumbers. It is in tropical seas, 

 however, that these animals most abound, where they lie in the mud or the 

 shallows, or crawl over the coral rocks. The surface of their bodies is com- 

 posed of a dense, tough, leathery skin, capable of being dilated or contracted, 

 lengthened or shortened, at the will of the animal. No stony shell is deposited 

 upon their bodies ; nevertheless, their relationship to the urchins and star- 

 fishes is manifestly shown by their apparatus of locomotive suckers, which 

 are of precisely the same structure as those of the Echinus. As if, however, 

 also to manifest an affinity with the Polype forms, there still exists in the Ho- 

 lothuria a circle of branched tentacles, which surround the mouth. These 



t 6\o66vpioj>, holothourion, a name applied by Aristotle. 



