nrvisioN or aximat.s. 76 



to collecting them into a superior order, according as we find ourselves 

 conducted to that classification hy a view of the whole of their attri- 

 butes. The second, and that which the greater part of modern natu- 

 rahsts have employed, is to fix beforehand upon certain bases of divi- 

 sions, agreeably to which, beings, when observed, are arran^^ed in their 

 proper places. 



The first mode cannot mislead us; but it is applicable only to those 

 beings of which we have a perfect knowledge: the second is more ge- 

 nerally practised, but it is subject to error. When the ba'^es that have 

 been adopted remain consistent with the combinations which observa- 

 tion discovers, and when the same foundations are again pointed o\it 

 by the results deduced from observation, the two means are then in 

 vmison, and we may l)e certain that the method is good. On the ana- 

 tomy of animals, science is most deeply indebted to the learned, acute, 

 and indefatigable Cuvier, who has contributed more than all others, 

 (save Hunter,) to our accurate knowledge of the characters on which 

 the classes are foimded. The whole animal kingdom is by Cuvier 

 divided into four great types : — 



1st. That of the animals which have their brain and the principal 

 part of their nervous system inclosed within vertebrse, and their mus- 

 cles attached to a bony skeleton. _ _ - - Vertebrosa. 

 2dly. Those that have no skeleton; whose muscles are attached 

 -to their skin, and whose nervous system is irregular in its form and 

 distribution. __-____- Mollusca. 

 3dly. Those that have no skeleton ; whose muscles are attached to 

 their skin, which is hard, or to processes proceeding from.it; and whose 

 nervous system consists of a series of knots or ganglia, brought into 

 commimication by two longitudinal nervous cords. - Anxulata. 

 4thly. Those whose bodies are radiated, and in whom no nervous sy- 

 stem has ])een discovered, and who have but one opening for the recep- 

 tion and rejection of their food. - - Radiata or Zoophytes. 



The animals which come under my observations in this work, be- 

 long to the type Annuluta, and the classes to which they belong may 

 readily be distinguished by the following characters. 



* Gills for reftpiration. Classes. 



Legs sixteen: antcnme two or four. - - 1. Crustacea. 



** Sacs fur respiration. 

 Legs twelve: antennee none : - - - 3. Arachkoidea, 



■*** Trachea for respiration. 



a. No antenna. 



- - 4. Acari. 



b. Tuo antennte. 



Six thoracic legs : abdomen also bearing legs: - 2. Myriapoda. 

 Six thoracic and no abdominal le9;s - - 5. Iksecta. 



