200 



ZOOLOGY. 



374. The vertebrate animah resemble man in the more 

 important points of their structure ; almost all the parts of their 

 bodies are in pairs, and disposed symmetrically on the two sides 

 of a median longitudinal plane ; their nervous system is highly 

 developed, and is composed of nerves and ganglions, and of a 

 brain and spinal marrow. To these we may add, that the 

 principal muscles are attached to an internal skeleton 

 (Fig. 138), composed of separate pieces, connected together, 

 and disposed so as to protect the more important organs, and 

 to form the passive instruments of locomotion ; that the more 

 important part of this skeleton forms a sheath for the brain 

 and spinal marrow, and results from the reunion of annular 

 portions, called vertebrae ; that the apparatus for the cir- 



Fig. 139. Nervous System of 

 an Insect (Carabus of the 

 Garden). 



Fig. 140." 



culation is very complete, and that 

 the heart offers at least two distinct 

 reservoirs; that the blood is red ; that 

 the limbs are almost always four in 

 number, and never more ; finally, that 

 there exist distinct organs lodged in 

 the head for sight, hearing, smell, and 

 taste. We have instanced man and 

 the dog as specimens of this type, but we may also include 

 the bird, the reptile, and the fish. 



375. Annulated Animals, or Entomozoaria. In the 

 second primary division of the animal kingdom we find a 

 general mode of conformation quite different from the pre- 

 ceding. The body is still symmetrical and binary, as in the 

 vertebrate animals, but it is composed of a series of parts 



Ideal section of the body of a lobster or craw-fish : e, the stomach, under- 

 neath which may be seen the gullet and the mouth ; , intestine ; f t the liver ; 

 . the heart ; c, cephalic nervous ganglions situated before and above the 

 gullet ; g, thoracic and abdominal ganglions situated below the alimentary 

 canal. 



