Heredity. 159 



there is no a priori improbability against an environ- 

 mental influence of some strength saturating* through 

 the entire organism, affecting one system by another, 

 till eventually the reproductive cells share in the change. 

 Weismann does not hold that the germ-plasm leads a 

 charmed life in the symbiosis of the organism. It is 

 not insulated from the general metabolism, in fact the 

 germ-plasm may be stimulated to vary by nutritive 

 changes. But to admit this is very different from 

 admitting that a change in the body of a parent can 

 so specifically affect the germ -plasm that a similar 

 change, corresponding in direction though not in 

 amount, is inherited by the offspring. 



Apart from the general connectedness of the different 

 parts of the body, and the common medium of the 

 lymph and blood, it seems worth while to refer to the 

 frequent occurrence of protoplasmic continuity within 

 the system. In plants the intracellular connections by 

 means of protoplasmic bridges are wide-spread; this is 

 true in many cases in regard to the cells of animals. 

 This is one of the various possible ways by which influ- 

 ences might pass from body to reproductive organs. 

 That important influences, inciting change, pass in the 

 opposite direction is well known. But it must be clearly 

 understood that Weismann is quite willing to admit 

 that changes in the body may stimulate the germ-plasm 

 to change. 



It is useful, also, to recall the numerous experi- 

 ments which have been made on the determination of 

 sex. Take only one example, the familiar case of 

 Yung's tadpoles, where, by altering the quantity and 

 quality of the food, he was able, for instance, to raise 

 the percentage of females from the normal of about fifty 

 to the abnormal of about ninety. Here, then, an en- 

 vironmental influence, playing in the first place on the 

 nutritive system, saturated throughout the organism, 

 and affected the reproductive system so as to swing the 

 balance emphatically to the female side. General hyper- 

 trophy brought out of the primitive indifference an 

 emphatic predominance of females. In this case the 

 reproductive system was unquestionably reached, and 



