220 HABIT AND INTELLIGENCE. [cHAr. 



for instance, carnivorous teeth are necessarily united with 

 a carnivorous stomach ; extremities modified for swimming, 

 as in the seal or whale, are necessarily united with a form 

 of body also suited for swimming. Such as these may be 

 Func- called functional adaptations. Besides these are what may 

 structm-al ^^ Called Structural ada]jtatious : as, for instance, the adap- 

 adapta- tation of the form of the bones to the pressure of the 

 muscles upon them ; or the adaptation of the forms of all 

 the organs in a serpent's body to the elongated form of its 

 The form body. Functional and structural adaptations, of course, 

 rt i ^^^^^ ^^^^ each other, and cannot be rigidly separated : 

 deter- the forms and characters of the various parts of an organ- 

 thrrest,^ ism are determined by each other, and they are aU. col- 

 and all by lectively determined by the nature of the animal's life. 

 mal's life. Thus, a carnivorous life determines the existence of a 

 carnivorous organization ; a herbivorous life determines 

 the existence of a herbivorous organization: so of a ter- 

 restrial or aquatic life, and of endless other classes of 

 modifications. 

 This is Concerning this doctrine, the question is not whether it 



is true ; for there is no doubt whatever that every organ in 

 an organism must be adapted to all the rest, and all to its 

 mode of life : these truths are implied in all the facts of 

 organization, and no fact of organization can be under- 

 stood without bearing them in mind. The question is, 

 hut will it whether Cuvier's doctrine cdo7ic will suffice to explain the 

 the facts'? ^^^^^ of Organization : whether the organization of a species 

 can be referred to the conditions of its existence alone, or 

 whether it is a resultant from the conditions of its exist- 

 ence jointly with some law, or principle, of a totally 

 different and quite peculiar kind. Cuvier maintained the 

 former : he always asserted that the whole organization of 

 a species was directly referable to the conditions of its 

 "We must existence. But the necessity is now universally recognised 

 further ^^ admitting a modifying principle of a distinct kind 



principle, from this. 



The two laws — for I admit them to be true, though I 

 deny that they explain everything — the law, I say, that 

 eve^y part of an organism has its form and character deter- 



