ANIMAL KINGDOM. 303 



species even pass the greater part of their life on. land, and 

 like some Batracians visit the water only in their season 

 of love. 



The more complete developement of the above distri- 

 bution of the Annulosa into five groups, shall also be 

 reserved for a future chapter ; and at present I proceed 

 to consider whether we may be able to quit these ani- 

 mals for others, or, in short, to determine whether the 

 chain or series we have hitherto followed so closely must 

 here end. 



As in the Vertebrata we have seen the internal skeleton 

 both bony and soft, so the external skeleton of Annulose 

 animals is likewise of various textures. In a worm or 

 caterpillar it is soft and membranaceous ; in a coleopterous 

 insect it is hard and horny ; in most Crustacea it is crus- 

 taceous, though in some of the Entomostraca it is even 

 testaceous. There are few animals so common and so in- 

 teresting, of which we know less than of these testaceous 

 Crustacea, if I may use the expression. Dr. Leach, who 

 is generally understood to be better acquainted with 

 the Crustacea than any other person now living, has 

 lately, in a most elaborate paper on the Entomostraca 

 of Miiller, published in the Dictionnaire des Sciences 

 Naturelles, proclaimed the group to be an "assemblage 

 artijiciel d'une portion de la classe des Crustaccs." Where 

 he has been unable to detect the order of nature I 

 can think it no disgrace to fail. I shall therefore keep 

 together this artificial assemblage, with the exception 

 of the greatest part, if not all, of the Branchiopodes pa- 

 rasites of Lamarck, which belong, as I imagine, to the 

 Ametabola. For the rest, I shall content myself at pre- 

 sent with a brief description of some of the Monoculi of 



