104 



RELATIONS OF MAN WITH EXTERNAL NATURE. 



far as his knowledge extended, founded by Cuvier, on anatomical characters. 

 Imperfect knowledge led him, however, to an imperfect separation or group- 

 ing of these in certain instances. The results of modern investigations are 

 embodied in the following table of the subkingdoms and classes, which ex- 

 hibits the classification adopted by Huxley, with the single exception of placing 

 the Infusoria as a class amongst the Protozoa, instead of ranking them as 

 a more important independent group. The subkingdoms, seven in number, 

 and the classes, twenty-six in number, are arranged on a similar plan to that 

 already adopted in regard to the Cuvierian system, so that the two may be 

 readily compared. 



Modern Arrangement. 



1. VERTEBRATA. 



Mammalia. 



Aves. 



Reptilia. 



Amphibia. 



Pisces. 



2. MOLLUSCA. 



Cephalopoda. 



Pteropoda. 



Pulmogasteropoda. 



Branchiogasteropoda. 



Lamellibranchiata. 



3. MOLLUSCOIDA. 



Ascidioida. 



Brachiopoda. 



Polyzoa. 



4. ANNULOSA. 



Insecta. 



Myriopoda. 



Arachnida. 



Crustacea. 



Annelida. 



5. ANNULOIDA. 



Scolecida. 

 Echinodermata. 



6. CQELENTERATA. 



Actinozoa. 

 Hydrozoa. 



7. PROTOZOA. 



Infusoria. 

 Spongida. 

 Rhizopoda. 

 Gregarinida. 



In explaining the advance of zoological knowledge as exhibited in these two 

 tables, attention may first be directed to the changes which have been made in 

 the smaller subdivisions or classes. The vertebrate classes have suffered the 

 least alteration the class Reptilia having been merely divided into the proper 

 Reptiles, such as the snakes, turtles, and lizards ; and the Batrachia or Am- 

 phibia, represented by the frogs and salamanders. Amongst the Mollusca, 

 the class of Gasteropods has been divided into those which breathe by lungs, 

 and those which respire by gills, i. e., into the Pulmo- and Branchio-gaster- 

 opoda. The class Acephala, .which included the testaceous and tunicated or- 

 ders of Cuvier, are subdivided into two corresponding classes, named the La- 

 mellibranchiata and the Ascidioida, the latter of which has been placed in a 

 new subkingdom. The class Brachiopoda has also undergone a similar trans- 

 position. The class Cirrhopoda, or barnacles, has been transferred as an 

 order to the Crustacea, belonging to another, the Annulose, subkingdom. Of 

 the Articulate classes, one order amongst the insects, named the Myriopoda, 

 is separated from them to form a distinct class ; whilst, as already mentioned, 

 the class Crustacea is reinforced by the Cirrhopods. The Radiate classes 

 have undergone the most notable changes, some of them having been much 



