PANGENESIS. 167 



a totally different developmental history. Hence wo 

 are led to believe in the complete independence of 

 " each structure from that which precedes and follows 

 it in the course of development," 



The functional independence of the elements or 

 units of the body. Variability and inheritance. — 

 Variability generally results " from changed conditions 

 acting during successive generations." The influence 

 is exerted on the sexual system, and if extreme, im- 

 potence tends to be produced. Bud-variation proves 

 that " variability is not necessarily connected with 

 the sexual system." The inherited effects of use and 

 disuse of parts imply that the changes in the cells 

 of a distant part of the body affect the reproductive 

 cells, so that the being produced from one of these 

 cells inherits the changes. " Nothing in the whole 

 circuit of physiology is more wonderful." 



" Inheritance is the rule and non-inheritance the 

 anomaly." Inheritance follows laws, such as the 

 tendency for a character to appear at corresponding 

 ages in parent and offspring. Reversion " proves to 

 us that the transmission of a character and its 

 development .... are distinct powers." Crossing 

 strongly induces reversion. " Every character which 

 occasionally reappears is present in a latent form in 

 each generation." 



The hypothesis of pangenesis attempts to explain 

 and connect together all the facts and conclusions 

 which have been summarised in the preceding pages. 



