88 



COLLEGE ZOOLOGY 



are the cranial, spinal, and autonomic 

 nerves. The autonomic nerves innervate the 

 heart, glands, and smooth muscular tissue. 

 They are influenced by the emotions, but 

 are not under the control of the will. 



Reproductive system 

 (reproduction) 



The essential organs of reproduction are 

 the ovaries, in which eggs develop, and the 

 testes, in w^hich the sperms are produced. 

 Accessory organs include those that supply 

 yolk and other secretions, ducts that carry 

 the germ cells or young to the outside, and 

 copulatory organs necessary to insure fer- 

 tilization. 



Putty 



Ball 



-Amoeba 

 Asymmetry 



Volvox 



Spherical 

 (Universal) 



FORMS OF ANIMALS 



Differences in the forms of animals are 

 due principally to differences in symmetry, 

 metamerism, and the character of the ap- 

 pendages. 



Symmetry 



Symmetry refers to the arrangement of 

 parts in relation to planes and straight lines. 

 Animals are either symmetrical or asym- 

 metrical (Fig. 44). The symmetrical ani- 

 mals may be divided into three types: (1) 

 spherically (universally) symmetrical, (2) 

 radially symmetrical, and (3) bilaterally 

 symmetrical. 



Canister 



Boat 



Hydra 

 Radial 



Man 

 Bilateral 



FiGtniE 44. Types of symmetry in animals; illustrated by common objects. 



