THE CLASSIFICATION OF ANIMALS. I33 



not developed: Alimentary Otma/., surrounded by a body-cavity; 

 distinguished into successive regions called pharynx, gullet, 

 crop, gizzard, and stomach-intestine, and possessing a separate 

 and posterior excretory aperture (anus) : YasavAar System, 

 containing colourless corpuscles in a red fluid, and consisting 

 of several main longitudinal trunks, of which the chief, 

 supra-intestinal and supra-neural, are connected in the 

 anterior region by six pairs of vessels : Excretory System, con- 

 sisting of paired tubes called nephridia or segmental organs, 

 lying in successive segments : Reproductive System, consisting 

 of male and female organs, both present in every individual. 



The metamerism of the body is indicated in the following 

 particulars : ringed muscular walls of the body, marking oS 

 successive segments ; successive ganglia of the longitudinal 

 ventral nerve-cord; presence of the segmental organs in 

 successive segments ; partitions across the body-cavity, called 

 mesenteries, which keep the alimentary canal firm in its place, 

 and correspond with the boundaries of segments. 



Development. The development, as just stated, is direct, no 

 larval form being developed. The student must refer to 

 Folygordius (p. 179) for a type of the development of the Vermes, 

 which throws light on the formation of the mesoblast and 

 body- cavity. 



Habits. The Earthworm is a burrowing terrestrial animal, 

 several inches long, which lives on leaves, vegetable mould, 

 and the small organisms contained in it. It is nocturnal, 

 coming to the surface of the ground at night. 



Place in classification. Sub-kingdom Vermes ; class 

 Annelida, sub-class Ohobtopoda; order Oligocliceta; sub-order' 

 TerricolcB; fa,m.ily LumbricidcB ; gernis Lumhricus. 



Detailed description. See Huxley and Martin's " Elementary 

 Biology"; Howes' "Atlas of Practical Elementary Biology"; 

 Marshall and Hurst's " Practical Zoology," and Thomsoh's 

 " Outlines of Zoology." For description of Pohjgordms and 

 its larva, see Parker's "Elementary Biology." 



