150 



EAPDWICKE'S SCIENCE-GOSSIP. 



[July 1, 1870. 



preserve, except those well coated with hair, which 

 they would hardly venture to attack. The cater- 

 pillars which agree best together are, of course, 

 those which are termed "Gregarious," or 

 " Sociable." At times individuals belonging to 

 some species which inflict singular injuries upon 

 each other. The well-known " Puss " larva will 

 nibble off the anal horns of a brother at a moment 

 when he is reposing ; and the larva; of the 

 Sphangine will also attack the horn which ornaments 

 the extremity of the body in various species, when 

 they have a chance. There are, in fact, endless 

 diversities observable in the habits of larvse, and the 

 study of them affords much amusement, and some- 



thing more. 



J. P. S. Clifford. 



SEA-URCHINS. 



AS summer draws on, and those who are able to 

 afford the luxury, begin to dream of with- 

 drawing for a while to the sea, inquiries for a sea- 

 side book, useful and entertaining, will make them- 

 selves heard. In prospect of such an event, we 

 commend [the one with its title at the foot,* and 

 from which we proceed to quote what the author 

 has to say about sea-urchins. 



The sea-urchins are enclosed in a calcareous kind 

 of shell, which is generally globular, or egg-shaped, 



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Fig. 132. Astrophyion verrucosum. 



The Asterias resemble stars ; the Echini, or sea- 

 urchins, may be likened to melons, yet both belong 

 to the same class, the Echinoderms. 



* " The World of the Sea," translated and enlarged by the 

 Rev. H. M. Hart, M.A., from " Le Monde de la Mer," by 

 Mons. Moqnin Tandon. London: Cassell, Petter, & Galpin. 

 The illustrations to this notice kindly lent by the publishers. 



Fig. 133. Penfarrinns EuriipcBus. 



but sometimes flattened. This shell, or carapace, 

 is really built up of polygonal plates, which adhere 

 by their edges to each other. The 

 plates are so arranged that the shell is 

 divided into vertical zones ; hence its 

 resemblance to the melon. These 

 zones are of two kinds, one being very 

 much larger than the other ; the plates 

 of the larger zones are covered with 

 sharp spines, which are movable, and 

 serve at once for protection and loco- 

 motion. The plates of the smaller zones 

 are pierced with pores, from which 

 issue filaments, by which the animal 

 breathes and walks. 



In the edible sea-urchin (Sphmre- 

 chinus esculentus) the she'll is composed 

 of 10,000 distinct pieces, so admir- 

 ably and firmly united that the whole 

 appears but one piece. The prickly 

 spines are often very numerous ; they 

 cover and protect the shell. From 

 these bristles the animal has been 

 named the " Sea Hedgehog." Its 

 scientific name is derived from txivoQ, 

 which was given to the creature by 

 Aristotle, from the evident resem- 

 blance the shell of the echinus, denuded of its 

 spines, bears to a " vase." 



In one species, as many as 2,000 bristles have 

 been counted ; in the edible sea-urchin there must 

 be at least 3,000. These appendages entirely cover 

 and hide the calcareous tunic whieh envelopes the 

 animal, like the numberless pearls which covered 



