THE INSTABILITY OF THE HOMOGENEOUS. 429 



become the one a fish, and the other a reptile, it cannot tell 

 us. That from two different eggs placed under the same 

 hen, should respectively come forth a duckling and a 

 chicken, is a fact not to be accounted for on the hypothesis 

 above developed. We have here no alternative but to fall 

 back upon the unexplained principle of hereditary trans- 

 mission. The capacity possessed by an unorganized germ of 

 unfolding into a complex adult, which repeats ancestral 

 traits in the minutest details, and that even when it has been 

 placed in conditions unlike those of its ancestors, is a capa- 

 city we cannot at present understand. That a microscopic 

 portion of seemingly structureless matter should embody an 

 influence of such kind, that the resulting man will in fifty 

 years after become gouty or insane, is a truth which would 

 be incredible were it not daily illustrated. Should 



it however turn out, as we shall hereafter find reason for 

 suspecting, that these complex differentiations which adults 

 exhibit, are themselves the slowly accumulated and trans- 

 mitted results of a process like that seen in the first changes 

 of the germ; it will follow that even those embryonic 

 changes due to hereditary influence, are remote conse- 

 quences of the alleged law. v Should it be shown that the 

 slight modifications wrought during life on each adult, and 

 bequeathed to offspring along with all like preceding modi- 

 fications, are themselves unlikenesses of parts that are 

 produced by unlikenesses of conditions; then it will follow 

 that the modifications displayed in the course of embryonic 

 development, are partly direct consequences of the insta- 

 bility of the homogeneous, and partly indirect consequences 

 of it. To give reasons for entertaining this hy- 



pothesis, however, is not needful for the justification of the 

 position here taken. It is enough that the most conspicuous 

 differentiations which incipient organisms universally dis- 

 play, correspond to the most marked differences of condi- 

 tions to which their parts are subject. It is enough that the 

 habitual contrast between outside and inside, which we 



