THEORY OF BROOKS. 2/7 



arity of the parent, either congenital or acquired, 

 might be inherited by the child. 



Theory of Brooks. 



A more recent theory requires more extended 

 notice, since it not only attempts to explain heredity, 

 but also variation ; and not only variation, but simul- 

 taneous variation affecting just those parts which 

 need change. If this theory can expain the occur- 

 rence of numerous simultaneous changes in those 

 organs which need change, and can demonstrate the 

 inheritance of the effects of use, it is plain that a 

 large portion of the difficulties which have arisen in 

 the way of all theories are removed. The theory in 

 question is that of an American scientist, Brooks, 

 and is in some respects a combination of all the 

 others, but chiefly of the pangenesis of Darwin and 

 the theory of Weismann. Brooks takes into account 

 the two sexes, believing that they have a different 

 share in heredity. Like Weismann, he explains 

 heredity proper by an appeal to the division of the 

 ovum. He also would say that early in the devel- 

 opment, the ovum becomes separated into two 

 parts, one of which develops into an embryo imme- 

 diately, while the other remains dormant in the ovary 

 of the developing individual until maturity, when it 

 in time goes through its development. It may, 

 meantime, of itself, divide into many parts, each 

 like every other, so that the ovary may at maturity 

 contain many similar ova. Heredity is then due to 

 descent from the same ovum, and if the ovum were 

 the only factor to be considered, every child would 



