68 ECHINODERMATA. 



The surprising mutilations incidental to some of the race may ut- 

 terly mislead one naturalist desirous of comparing his own remarks with 

 the narrative of another, or with the figures presented to his view by 

 preceding authors : Nor is it from external appearance alone that he 

 shall be exposed to error, for, on careful dissection, he may be disap- 

 pointed of finding those internal organs known to distinguish his subject 

 from all its fellows, -they have been lost by one of those extraordinary 

 processes, natural or unnatural, above described, to be regenerated with 

 the lapse of time, provided the survivance of the animal should be suffi- 

 cient to admit of it. 



Therefore it is essential that due attention be invariably paid to 

 perfection, vigour, and the most favourable conditions of existence, and 

 that nothing should be overlooked in representation. 



I have repeatedly failed in my attempts to identify various species 

 of the Holothuria falling into my possession, with those described by 

 other authors, though the difference was apparently inconsiderable. 

 Without presuming any inaccuracy on their part, I would rather tax 

 myself with some oversight, and supply my deficiencies by correct deli- 

 neations, along with descriptions, which might be the best means of 

 attaining the truth. Wanting such auxiliaries, which are truly substi- 

 tutes for real specimens, most of the subjects of natural history of rare 

 occurrence, or, in fact, that may not be daily before us, must prove un- 

 intelligible. 



There are numerous sources of embarrassment, nor do all originate 

 from the different views of different naturalists. I have failed to iden- 

 tify certain subjects of rare occurrence with those familiar to me, either 

 from defective organization, or supervening injuries and decay. I could 

 not pronounce them the same, though personally satisfied that they were 

 not distinct. At the same time, such subjects were dead, and disfigured 

 for the most part, for equal embarrassment is seldom experienced with 

 living specimens of sufficient dimensions. 



On the 27th of February, a specimen of the Holothuria reached 

 me, which had been recently fished up from the sea. It was contracted 

 to about five inches in length, rather slender in proportion, and totally 



