136 DEVELOPMENT AND HEREDITY. 



combinations and co-ordinations which were always 

 becoming more and more complex. In the inter- 

 action of the environment on the individual, the 

 environment always remained the same, but the in- 

 dividual was constantly changed by the action of the 

 environment as each new development in the indi- 

 vidual brought it into a new relation with the 

 environment. Thus the life of the individual would 

 consist of constant growth and development. 



When now a small part of the living matter of 

 this individual separates from the main mass and 

 begins an independent existence, it cannot continue 

 the progress of development without a break ; for, 

 owing to its small size, and perhaps its lack of cer- 

 tain organs, the forces of the environment do not 

 act upon it in the same way as upon its full-grown 

 parent, and so the reactions of the small germ can- 

 not be the same. But the environment must act 

 upon the small germ almost exactly as it acted upon 

 the parent at that time when the parent was a small 

 germ of similar size and conditions. Thus the 

 second individual would follow almost the identical 

 course of development that the parent followed, and 

 so on, generation after generation. The continued 

 sameness of environment is the cause of the simi- 

 larity of successive generations. 



The unbroken continuity of living matter thus 



