120 CLASS CRUSTACEA. 



this singular creature is not a perfect animal, but merely 

 the larva, or imperfect state of the Common Crab. 

 This fact is perfectly new, and interesting in a double 

 point of view, not only proving their real nature, but 

 also that the Crustacea are not, as described in most 

 systems, animals undergoing no metamorphosis, and on 

 that account to be separated from the insects, but that 

 they do undergo a metamorphosis, and that of a most 

 wonderful nature. 



It was in the Spring of 1822 that Mr. Thomson first 

 met with Zoese, in the harbour of Cove, and that in 

 considerable abundance ; the year following, at the same 

 season, one of considerable size occurred; this was con- 

 sidered a fit object for experiment, and was carefully 

 supplied with fresh sea-water, from May 14th to June 

 15th, when it died in the act of changing its skin. 

 That portion of its new form which it had been able to 

 disengage was sufficient to show that it bore a great 

 resemblance to the division of the Crustacea, in which 

 the crabs and lobsters are placed. " This proof," says 

 the author, "might be considered incomplete, if I had 

 not had the good fortune to succeed in hatching the ova 

 of the Common Crab, during the month of June, which 

 presented exactly the appearance of the Zoea taurus.'' 



The Common Crab, Cancer major, is so well known, 

 that any description of its appearance would be useless. 



One singular part of the history of these creatures is, 

 the power that is possessed by them, of changing their 

 shell once in every year; this power is providentially 

 bestowed upon them, to enable them to increase in size, 

 a thing that would otherwise be utterly impossible, 

 from the peculiar nature of the hard coat in which they 

 are enclosed. 



