Miscellaneous . 213 



branching up from the lowest Infusoria to the higher grades of life. 

 It is not true that the forms among the lower grades are actually 

 copied in any of the imperfectly developed young of the superior ; 

 yet there is some general analogy, sufficient to indicate that the 

 former commence on the same system of development with some of 

 the latter, although carried essentially out of the direct upward line 

 by the peculiar vital forces of the species. The Rotifera are de- 

 cidedly crustacean in type. Their stout mandibles are precisely those 

 of the Cyclopacea in position, and also in general form ; and in their 

 mode of reproduction the animals are closely similar ; yet no young 

 crustacean is ever a Rotifer. The latter belongs to the same system 

 of development with the former, but is a distinct branch, from the 

 regular line, characterized by the peculiar natatory organs, which 

 appear to be the analogues of the branchial or basal appendages to 

 the feet in Crustacea. The same reasoning applies to the Bryozoa 

 or Flustroid polyps, which are as nearly allied to the Tunicata as 

 the Rotifers to Crustacea*. It is a side-development from the ima- 

 ginary line which connects the Infusoria with the tunicated mol- 

 lusks. The Entozoa afford other examples, one branch of them 

 passing into the Crustacea through the Lernceidce and Caligida, and 

 another into the Annelida. 



These remarks are intended to support no monad or Lamarckian 

 theory, but only to elucidate the established principle, that there are 

 in nature certain distinct systems or types of development. Each 

 species is developed with some reference to one or the other of these 

 systems, but through the agency of the vital forces peculiar to itself 

 — forces which there is reason to believe only creative power can 

 change. 



In accordance with these principles, the several orders of animals 

 may be arranged as follows : — 



I. Vertebrata. 



III. Articulata. 

 isecta, Myriapoda, 

 Arachnida, 

 Crustacea, Annelida. 



II. Mollusca. 



Insecta, Myriapoda, Cephalopoda, Pteropoda, 



Arachnida, 



IV. Radiata. 



Echinodermata. 



Gastropoda, Conchifera, 

 Tunicata. 



Rotifera, Entozoa. Zoophyta, Acalephse. Bryozoa. 



V. Protozoa or Infusoria. 



A radiated structure characterizes in general the simplest forms of 

 animal life. Passing up from the monad globule, this structure has 

 its highest development in the Echinoderms. Among Zoophytes, 



* The Bryozoa have been placed near the Rotifera; but the absence of 

 mandibles, as well as their peculiar type of structure, separates them widely 

 from these Crustaceoid species, and allies them as closely to the Tunicata, 

 with which they were first associated by Thompson, under the name of 

 Polyzoa. Lister has a finely illustrated article on this subject in the ' Phi- 

 losophical Transactions' for 1834, p. 365. 



