Aug. 1, 186S.] 



HAPDWICKE'S SCIENCE-GOSSIP. 



175 



ECHINODERM SPICULES. 



ECIIINODERMS constitute a class of marine 

 animals known to naturalists by the term 

 Echinodermata, which, literally interpreted, means 

 " hedgehog skinned," and some of its members do 

 really bristle with spines, like quills upon "the 

 fretful porcupine." The star-fishes, of which the 

 common "five-fingers " is an example, is an Echino- 

 denn ; the sea-urchin, or sea -egg, is an Echino- 

 derm ; and the sea-cucumber is an Echinoderm, 

 and so are the disgusting-looking sea-slugs, which 

 are eaten and considered a delicacy by the Chinese. 

 Our epithet of "disgusting" applies to them in 

 the dried, shrivelled, odorous condition in which 

 they appear in the Oriental markets, and now 

 and then in occidental museums. Eor our present 

 purpose it will serve to regard the class of Echino- 

 derms as made up of sea-urchins, star-fish, and sea- 

 slugs, or, writing more accurately and scientifically, 

 the Asteroidea as representing the star-fish, the 

 Echinoidea, including the sea-urchins, and the 

 IMothuroidea, or sea-slugs, and cucumbers. The 

 Sipunculoidea we will leave out of consideration. 



It is more especially in illustration of certain 

 microscopical objects derived from Echinoderms 

 that we have entered upon the subject. Every one 

 who has a collection of objects knows that the 

 «ections of the spines of the larger urchins are 

 beautiful, and already we have devoted an article to 

 the Purple urchin.* Then the little star-fish are 

 deservedly favourites, and to these we have also 

 directed the attention of our readers, both the 

 " claws of OpJiiocoma rosula " f and the body of 

 Ophiocoma neglecta, % and now it is to the calcareous 

 plates and spicules that we furnish a running com- 

 mentary, more with the view of directing attention 

 to the subject than by any means exhausting it. It 

 shall be our province rather to suggest than to 

 teach, and to indicate a direction for the researches 

 of any microscopist who may shortly be doomed 



Fig. 173. Spicules of 

 Echinus sphcera. 



Fig. 174. Spicules from 

 Mespiliu sp. 



to consume a month, and aught besides, at the sea- 

 side. 



In the last volume of the " Transactions of the 

 Linnean Society" was published a paper by Mr. 



* " The Skeleton of the Purple Urchin," by T. G. Ponton, 

 I867, p. 82. 

 t Science-Gossip, 1866, p. 202. % Ibid., 1867, P- 219. 



Charles Stewart, more especially devoted to the 

 plates and spicules of the Echinoidea, which will 

 well repay a perusal. Whilst the "C "-shaped 

 spicules are common in many urchins, as in our 

 indigenous species, the " common egg-urchin " 

 (Echinus sphcera), they occur also in the ambulacral 

 tube of a species of Mespilia; then in a species 



Fig-. 175. Spicules of 

 Echinus drobrachiensis . 



Fig. 176. Spicules 

 of Synapta from Japan. 



{Echinus drobrachiensis*), found on our northern 

 coasts, another and less regular figure occurs, some- 



Fig. 177- Spicules of 

 ovary of Echinometra. 



Fig. 178. Spicule from 

 mesentery of Eehinumetra. 



what like bent thigh-bones; similar, but larger 

 spicules being present in a species of Synapta from 



Fig-. 179. Spicules from 

 Mesentery of Cidaris. 



Fig. 180. Spicule of 

 Cidaris grandis. 



Japan. Still more irregular and indefinable forms 

 occur in the ovary and mesentery of an Echinometra, 



* Echinus nesrlectus of Forbes. 



