1 82 CLUES AND SUGGESTIONS CHAP. 



structure when compared with the mere 

 aggregations characteristic of crystalline 

 forms, does, indeed, make it impossible 

 to conceive that organic growths can be, 

 in fundamental principle, like that of a 

 crystal. But in the one circumstance, 

 or condition of determinatedness in the 

 direction of growth, a common feature 

 may undoubtedly be recognised. It is 

 quite conceivable that the " physiological 

 units " of all organic structures should be 

 under the control of a force which de- 

 termines their unknown movements and 

 mutual arrangements, so as to build up, 

 and form, the most complex structures 

 needed for future functions in distances 

 of time however far away. The truth 

 is that this conception is nothing more 

 than a bare description of the facts. It 

 supplies us with a far more simple and 

 conceivable explanation of the Cetacean 

 pelvis than the alternative suggestion 



