CH. xxiir.] THE CAUSES OF DEVELOPMENT. 293 



the causes already and independently known to exist are known 

 demonstrably inadequate to produce the eflects, that we 

 can with any certainty infer from the effects the existence 

 of distinct and separate causes. From this point of view, 

 the questions of the origin of species, and of organization, 

 may be thus stated : — 



Given the laws of the relation of life to matter and 

 energy — or, in other words, given the chemical and dyna- 

 mical properties of vitalized matter ; — given also the laws 

 of habit and variation : — are these, in combination with 

 the action of external causes, sufficient to account for the 

 facts of organization and morphology ? Will vitalized 

 matter assume organization under the action of external 

 forces, and in obedience to no other laws than chemical 

 and dynamical ones, and the vital laws of habit and 

 variation ? 



Before we endeavour to answer these questions, let us 

 go back on the subject, and recount what organization is. 

 Organization, as defined in a former chapter, is the adap- 

 tation of structure to function ; or, in other words, the Organiza- 

 adaptation of every part of an organism to every other adaptL 

 part, and of all to the mode of life of the organism. It is tiou, 

 obvious that if any theory of the origin of organization is morpho- 

 to be complete, it must account for histological as well as ii°ftoio-^" 

 morphological adaptations ; that is to say, it must not only gical. 

 account for the adaptation of the foot for walking, of the 

 hand for grasping, of the wing for flying, of the jaws for 

 masticating, and of other organs each for its own special, 

 work ; it must also explain how each different kind of 

 tissue has been formed and fitted for its function — bone for 

 support, muscle for transforming vital into motor energy, 

 and the other tissues of which organisms are built up, each 

 for its own peculiar function. These two problems, it is The 

 evident, run into each other ; nevertheless they are dis- twofold! 

 tinct : and it may be thought that the problem of the 

 origin of morphological adaptations — that is to say, the 

 adaptation of every organ to its particular work — is a 

 partly soluble problem; while the origin of histological 

 adaptations — that is to say, the adaptation of every kind of 



