Oct., 1845.] 



2S3 



fusoria with the Tunicated Molluscs. The Entozoa afford other ex- 

 amples, one branch of them passing into the Crustacea through the 

 Lernceidrc and Caligidae, and the other 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. 



Insecta, Myriapoda, 



Arachnida. 

 Crustacea, Annelida. 



II. MOLLUSCA. 



Cephalopoda,Pteropoda, 



Gastropoda, Conchifera, 



Tunicata. 



IV. Radiata. 



Echinodermata. 

 Rotifera, Entozoa. „ , . . , 



Zoophyta,Acalephse. 



Bryozoa. 



V. Protozoa or Infusoria. 



A radiated structure characterizes the simplest form of ani- 

 mal life. Passing up from the monad globule, the structure has 

 its highest development in the Echinoderms. Among Zoophytes, 

 the Hydra forms the first step upward, in which the digestive 

 cavity is a mere sac, which will work equally well inside out, and 

 the mode of reproduction is extremely simple. From this group 

 we pass to the Actinia, in which there is a distinct stomach and a 

 series of fleshy lamellae around the internal cavity — the first rudi- 

 ments of an insolation of the functions of digestion and generation — 

 but the circulating fluid is only the elaborated chyle mingled with 

 more or less water from without. A step farther and we find 

 separate organs for the functions of the liver, and a circulating 

 system, in some Echinoderms. Through the Bryozoa, the In- 

 fusoria are connected with the Tunicata and the other Molluscs ; and 



