CLASSIFICATION OF ANIMALS. 703 



* 



ECHINODERMATA. 



Star-fishes, sea-urchins, sea-cucumbers, and crinoids, 



ANNULOSA. 



Entozoa .... Tape-worms, etc. 



Rotifera .... Wheel-Animalcule. 



Annelida . . . . Worms, leeches. 



Cerripida .... Barnacles. 



Crustacea .... Shell-fish. 



Insecta .... Various insects. 



Arachnida .... Spiders, scorpions, etc. 



MOLLUSCA. 

 MULLOSCOIDA POLYZOA. 



Accphala or headless pupa. Encephala with head. 



Tunicata 



Brachiopoda 



Lamellibranchiata (bivalves). 



Pteropoda. 



Gasteropoda (univalves). 

 Cephalopoda, cuttle-fish, etc. 



VERTEBRATA. 



ICHTHYOPSIDA. 



Class I. Fishes. . . Various orders, 

 II. Amphibia . . Frogs, toads, salamanders, etc. 



SAUROPSIDA. 



\\\.Reptilia . . Tortoises, smaller snakes, lizards, etc. 

 I V. Birds . . . Various orders. 



MAMMALIA. 



Class I. Non-Placental . Marsupials. 



\\.-PlaceiitaL . Edentata, cetacea, ungulata, quadrumana, 



bimana, etc. 



We will adopt the latter order as being the more modern, and endeavour 

 to make the various classes of the invertebrates clear to the mind, if we 

 cannot present them to the vision, of the reader. 



In our sketch of Botany we remarked upon the similarity existing 

 between the cells of plants and animals, and although there are, of course, 

 differences, there are many points of resemblance in these cells. 



Plants have their lowest representatives called Protophytes. Animals 

 which correspond to this class are termed Protozoa, from the Greek, proton, 

 first, and soon, animal. The former are, as already mentioned, seen 

 amongst the algae, consisting of simple cells, and protozoa cannot easily be 

 distinguished from them except in the matter of nutriment, for some pro- 

 tozoa have no mouth except in the infusoria class. The cells are very 

 much alike, and Dr. Carpenter sums them up briefly as follows : 



" The animal cell, in its most complete form, is comparable in most parts 



