STRUCTURE OF ARTICULATA. 



11 



around this canal a sort of collar (d). 

 The different nerves of the body arise 

 from these ganglia and ramify in the 

 neighbouring parts. 



6. The organs of the senses are less 

 numerous than in vertebrate animals, 

 and sometimes they are altogether 

 wanting." In general they have eyes, 

 and sometimes an apparatus of hearing, 

 but no articulated animal has yet been 

 discovered possessing a distinct organ 

 of smell. It must not be inferred, 

 however, from this fact, that they are all 

 incapable of appreciating odours. 



7. The digestive tube or canal of 

 these animals is always extended from 

 one end of the body to the other (figs. 

 12 and 74), and the mouth is generally 

 furnished with jaws ; but these organs 

 do not move up and down as in verte- 

 brate animals ; they are always lateral, 

 and move from without inwards. 



8. In general their blood is white, but 

 not always ; in the class of anne'lida it 

 is red ; and its manner of circulating 



is various. In these animals the mode of respiration is equally 

 various. They are all ovi'parous, that is, their young are pro- 

 duced from eggs. 



9. Articulated animals, possessing, as they do, a nervous sys- 

 tem more developed than that of the rnollusks, limbs for locomo- 

 tion, and a sort of tegumentary skeleton, must necessarily be 

 superior to them in every thing which essentially characterized 

 ammatity, that is, in the functions of relation ; but, as respects the 

 functions of vegetative life, they are not so well provided ; their 



Explanation of Fig. 2. The nervous system of an insect : cr, the brain 

 or cephalic ganglion : 6, the optic nerves ; c, nerves of the head ; d, 

 nervous cords which unite the brain to the thoracic ganglia, and form a 

 collar around the oesophagus ; e, e, e, e, thoracic and abdominal ganglia ; 

 /, nervous cords which unite the nerves with each other ; jf, g, nerves of 

 different parts of the body. 



6. Are the senses perfect and complete ? Have articulated animals the 

 tense 'of smell ? 



7. What is the character of the digestive apparatus in articulated 

 animals ? 



8. What is the colour of their blood ? How do they breathe ? How are 

 they propagated ? 



9. In what respects are articulated animals superior to rnollusks ? 



Fig. 2. NERVES OF AM 

 INSECT. 



