408 PHYSIOLOGICAL DEVELOPMENT. 



the truth that both of the two great laws of evolution are 

 exemplified in the organic world as a whole, as they are 

 exemplified in every organism, and in all other things. 



The reader has long since become familiar with the gene- 

 ralization that while Evolution is a change from the homo- 

 geneous to the heterogeneous, it is also a change from the 

 incoherent to the coherent; and this change from the inco- 

 herent to the coherent has been above exhibited as going on 

 even throughout that vast assemblage of organisms, plant 

 and animal, which cover the Earth's surface. In what we 

 are obliged to conceive as the earliest stage, when the most 

 minute types of life alone existed, the aggregate of living 

 things was at once homogeneous and incoherent. In the 

 course of epochs immeasurable in duration, this uniform 

 aggregate of beings has been becoming more multiform. 

 And now we see that instead of forms of life everywhere 

 without the slightest union caused by mutual dependence, 

 there have slowly arisen forms of life among which mutual 

 dependences have entailed vital connexions correspondingly 

 marked. Along with progressing differentiation there has 

 ever been progressing integration. So that we may recog- 

 nize something like a growing life of the entire aggregate of 

 organisms in addition to the lives of individual organisms 

 an exchange of services among parts enhancing the life of 

 the whole. 



In this final generalization the law of Evolution is mani- 

 fested under its most transcendental form. 



