1 



THEORIES OF HEREDITY 1 5 



• 

 their school teach that acquired characteristics 

 are transmitted. Datwin supported the doctrii^ 

 by his hypothesis of pangenesis. Very sm^ 

 particles, he thought, infinitesimal in size, are 

 constantly thrown off from all the cells of the 

 body ; " these particles collect in the reproductive 

 cells, and hence any change arising in the organ- 

 ism at any time during its life is represented in 

 the reproductive cells." ^ The moment an ex- 

 planation of the process by which characteristics 

 are transmitted is attempted, the difficulty of the 

 problem is apparent. Thus it is said, that there 

 is growing up in our time a race of near-sighted 

 men and women. The clear vision of the days 

 when our ancestors roamed the forests and were 

 dependent on the sense of sight for protection 

 has disappeared. The habit of seeing objects at 

 short range in course of time made many men 

 near-sighted ; they handed down the peculiarity 

 to their children, who increased it, and in turn 

 transmitted it, and so congenital near-sightedness 

 became common. In the same way the presence 

 of disease in many families is accounted for, and 

 also the possession of exceptional gifts of body 

 and mind. In the opinion of these masters of 



1 TAe Variaiion of Animals and Plants under Domestication, 

 Darwin, Vol. II. pp. 349-399. 



