1899] LAMARCK'S THEORIES 291 



view the functional life of living things, and endeavour to understand 

 clearly the true nature of a function. A function is the use which an 

 organ serves. All living things possess organs, the uses of which are 

 called functions. Moreover, there are functions which require, not 

 only their proper organs, but also other auxiliary organs for their 

 effective performance. But functions, and hence organs, vary in im- 

 portance. There are certain functions so highly important to life and 

 the propagation of the species, that special centres in the central 

 nervous system are found to preside over and control them, giving 

 origin to the need or desire for satisfying them. Such functions are- 

 nutrition, reproduction, and, to some extent, protection, and it is in 

 response to the need or desire of the organism that such functions are 

 satisfied. 



It is doubtful if any one will be found to dispute the importance 

 of those functions, or their connection with the need or desire emanat- 

 ing from the brain for their satisfaction. 



Now it is held as a truism by biologists that " the function makes 

 the organ." That this is so must withstand any attempt at refutation, 

 for it is inconceivable that the organ was first to appear, to be sub- 

 sequently followed by the function. Stress is laid on this jtoint, 

 because the whole interpretation of Lamarck hangs on its recognition. 

 Further, we can well understand that the nature of the function, i.e. 

 the manner in which the need or desire presiding over the function is 

 satisfied, determines the structural nature of the organ. Change the 

 method of satisfying the function and we may change the structural 

 nature of the organ. But we must also remember that the most im- 

 portant functions have not only their proper organs, but also other 

 auxiliary organs which are brought into new uses when the methods of 

 satisfying the functions are changed. If, e.g., an animal subsisting on 

 surface vegetation, etc., be driven to climb trees in order to satisfy its 

 desire for food, as it is said the mongoose in Jamaica now sometimes 

 does, while the true organs of nutrition will doubtless undergo little if 

 any change, yet, if the habit through any cause, such as continuous 

 drought, etc., be fully established, the auxiliary organs — the feet and 

 claws — will gradually be modified until they serve fully the function 

 of nutrition, i.e. until the feet -and claws fully serve the purpose of 

 procuring food. We should then get undoubtedly, in the case of the 

 mongoose, a change towards a squirrel-like type. We thus learn how 

 correlated are different and distant organs in maintaining the integrity 

 of the most important functions. 



Bearing the above facts in mind, we are now prepared to consider 

 the theories of Lamarck. These theories he condensed into certain 

 formulas and laws, which are as follows : — 



(1) "That every change which is at all considerable and continu- 

 ously maintained in the circumstances of each race of animals, effects 

 in it a real change in their needs." 



