124 THE BIOLOGY OF AN ANIMAL. 



Since living matter undergoes incessant waste of material by 

 oxidation (p. 4), and is continually expending energy (p. 33), 

 the earthworm must be replenished with matter and energy in 

 the form of ordinary food (Alimentation] and oxygen (Respira- 

 tion in part). The new matter must be distributed to all parts 

 of the organism (Circulation}, and after its incorporation into 

 the living substance and ultimate decomposition for the liberation 

 of energy (Metabolism) the results of decomposition must be 

 eliminated from the body (Excretion; Respiration in part). 

 Again, every animal possesses some power of Motion either as a 

 whole or in some of its parts. The movements as well as all the 

 other vital actions must be guided and controlled (Co-ordination}. 

 The organism must be capable of receiving impressions from the 

 external world, and of perceiving changes in or near itself (Sensa- 

 tion in the broadest sense). And besides the above-mentioned 

 requirements there are a number of subsidiary needs, such as the 

 support and protection of the soft and delicate structures of the 

 body ; means of offence, defence, etc. (Support, Connection, Pro- 

 tection, etc.). Lastly, since individual existence is limited, pro- 

 vision must be made for the perpetuation of the race (Reproduc- 

 tion^). 



These ten primary functions fall at once naturally into two 

 groups, since the first nine relate to the existence of each indi- 

 vidual, while the tenth concerns the individual only as a member 

 of the race of earthworms. The nine individual needs may in 

 turn be arranged in two groups, viz., Nutrition and Relation. 

 The former (Alimentation, Circulation, Metabolism, Respiration, 

 and Excretion) are concerned especially with the income, trans- 

 formation, and outgo of matter and energy in the organism. The 

 latter (Motion, Co-ordination, Sensation, Support, etc.) have to 

 do especially with the mechanical relations of the various parts 

 of the organism to one another and to the environment. 



The machinery by whose action the primary functions are performed 

 varies widely in different animals even for accomplishing the same func- 

 tion. For instance, the single function of Kespinii i<m is performed by four 

 quite different mechanic-ill arrangements in earthworms, beetles, fishes, and 

 men, respectively. Locomotion (a special case of motion) is effected by dif- 

 ferent mechanisms, according as it occurs in earthworms, jelly-fishes, but- 

 terflies, or horses. 



Sometimes the machinery assumes the form of simple cells, as in the 



