25 Experiments and Ohftr-vatlons 



Jlxpoimaits on the covering Suh fiance of CruJIaceous Mmine 

 Animals *. 



As I was not acquainted with any experiments by Vvhich 

 the cbcrnical nature of the lubilance which covers crufta- 

 ceous marine animals had been determined, I was defirons 

 to afcertain in what refpeft it was ditfcrcnt from (liell ; and 

 1 began tliefe experiments on three fpceies of the echinus, 

 with which F had been favoured by tlie Right Hon, Prefidenl. 



I was the more inchned to begin with the echini, bccaufe 

 naturalirts do not appear to be perfcc^tly agreed whether ttf) 

 call them teftaceous or crullaccous animals. 



Klein, who has written a work upon echini, after having 

 noticed the various opinions of Rondelet, Rumphius, and 

 others, determines that thej'^ are to be regarded as teilaceous 

 animals. His words are : " Sic plurimas teftas marinas, in 

 '•■ ftatLi naturali confideratas, cum eehinodermatis potiusquani 

 " cum cruftis aftacorum vel cancrorum conferre llcebit. Ita- 

 " que echinodcrma cum Ariftotelc qui cchhios inter teftacca 

 " quibus facullas ingrcdicndi ell: reponit, ncc non cum Be- 

 •' lonio, Aldrovaudo, et cxccllentillimo SJoanlo religiofe fcf- 

 "■ tam appdlymus, quam fatis duram in noimullis oflendi- 

 " inns t." 



But Linn;eus was of (he contrary opinion, as appears from 

 liis definition of the echinus: " Corpus fubrotundum cruJliZ 

 " <jlTc'a tcdum fpinis mobilibus f?epius afpera]:." 



Now, as the experiments above related had proved that 

 the lliells of marine animals were compofed of carbonate of 

 hme, witIi.out any phofphale, I thought it very poflible tliat 

 tl)c covering of the crufiaceous animals might, in fome re- 

 fpcift, be dificrent; ami if fo, I fliould thus, by chemical 



rli.; ihops have proved that the term boue is here mifapplicd, if the prc- 

 <euj;-e of piiorphw^ of Jimt is to be regarded as the charafteriftic of bonu ; 

 for this fub.'Unce in ctimpofition is exatlly fimilar to fliell, and confifts cf 

 ^vnrious membrants hanitncd by carbonate of lime, without the fmalleft 

 unxturc of pUii'phte. 



• Untkr this head I hav? Jiichide<\ my experuTients upon echini, ftar- 

 toi)\, crab's, tob.Urs, &c. 



■<- KU-in liatHral'ii Difpofitin Ei-hinorl^rm/iium, Sec. p. lo, 



J Byjlema l^nuiree. Edit, Gmthn, (>. jifro, 



charafters, 



