§ 5. DIVERSITY OF ANIMAL FORMS. 595 



But the nerves not only bestow feeling, they also confer 

 the power of voluntary motion ; and if the organs to which 

 the motor nerves proceed be suitably constructed, they 

 enable the animal to effect progression, or in other words, 

 to change its situation from one place to another. As 

 we descend in the scale of creation, we find many animals 

 destitute of that power, and living on the same spot 

 from the commencement to the termination of their 

 existence; and all these creatures are inhabitants of 

 the water. 



Such, then, are the essential characters of animals — 

 an external determinate form, gradually developed, with 

 an internal organization possessing vessels for effecting 

 nutrition and support, and capable of attracting and assi- 

 milating particles of inorganic matter ; combined with 

 a nervous system communicating sensation and voluntary 

 motion ; a certain term of existence being assigned to 

 determinate forms — in other words, a period of life and 

 death. 



5. Diversity of Animal forms. — Animals are as varied 

 in form and magnitude as the imagination can conceive ; 

 from the god-like image of Man, to the globule of jelly that 

 floats upon the wave — from the Elephant and the Whale, 

 to the Insect and the Animalcule, of which millions may be 

 contained in a drop of water. In fact, so numerous and 

 dissimilar both in form and structure are the animal organ- 

 isms that exist on the earth, that the opinion of Astronomers 

 that the inhabitants of the worlds around us, must, from 

 the different densities and conditions of the respective 

 planets, be totally distinct and unlike any that are known 



effects produced by the latter — though a very general, is not a constant 

 character ; for some animals evolve oxygen : and from all the parts of 

 plants which are not green, carbonic acid is exhaled : and when light 

 is removed from the plant, the same thing happens every where. See 

 Br. Bence Jones's Gulstonian Lectures, for 1846. 

 VOL. II. R R 



