140 CRUSTACEANS. 



them. Farther, that the closer the elements of discussion are concen- 

 trated, their purport will be more con^dncing. 



The Crustaceans form an immense class among the animals invested 

 by a firm, resisting, integumentary covering, of a certain quality, which, 

 mostly dwelling in the waters, are extensively distributed throughout 

 the globe. They are distinguished by the greatest variety of appearance, 

 disparity of size, modification of form, and peculiarity of habits, whence 

 many doubts are entertained whether some are properly enrolled here, 

 or should be discarded to other places. 



As yet, they are but imperfectly known. Few have been watched 

 in their living state, and scarcely any preserved, as the subject of care, 

 for permanent observation. Thus, unless with rare exceptions, the}^ 

 have seldom fallen within the sphere of the physiologist : and at this 

 moment, the most interesting points in the history of many, are as little 

 understood as they were in the days of Aristotle. 



The Crustacea are never represented ahve, in the exercise of their 

 natural functions, or as embeUished bj^ their natural colours ; because it 

 is believed that they are less exposed to alteration by death. 



Of later years, the mere classification of multitudes of these crea- 

 tures, and recording their synonyms, seem to have been chiefly contem- 

 plated by modern authors, which is of considerable utility. 



But this is not enough for the inquisitive, who demand information 

 of their nature. 



With infinite deference to those naturalists of superior attainments, 

 who may have embarked in similar enquiries ; and with an anxious 

 desire to avoid interference with their peculiar pursuits, I venture to 

 offer a few results from personal observation. 



Comprehending a multitude of living creatures, externally void of 

 any common resemblance, under the name of Crustacean, seems entirely 

 a modern contrivance, derived from the nature of their integuments. 

 Their flesh is very scanty ; and instead of the skin usually protecting 

 animals, they are invested, wholly or partially, by a shelly covering. 



The nature of this covering leads to several singular physical con- 

 sequences. Being inflexible, it does not enlarge with the life of the 



