GROWTH AND REPRODUCTION 61 



to intensity, and that it is impossible for somatic 

 changes to be transmitted telegraphically to the 

 germ cells, to be developed later in the course of 

 ontogeny. Such a process he cleverly compares to 

 a telegram sent in German and arriving in Chinese. 

 If it be true that all nervous impulses are identical 

 in quality, this would seem a serious objection to the 

 mnemic theory. But this is by no means proven. 

 It is a fact that a motor nerve, like the spinal acces- 

 sory, can be cross-grafted so that the impulses going 

 through it will act in the territory of the facial nerve. 

 When we take the case of the nerves of special sense, 

 however, we find such great differences in the quali- 

 ties of the sensations that it is simpler to admit the 

 existence of differences in impulse quality than to 

 find any other way out of the difficulty. 



It would be useless here to enter further on the 

 comparison of the Weismann and Hering-Semon 

 theories of inheritance. Both have their strong 

 points and both have their weaknesses. Weismann's 

 theory is strong where it attempts to explain the 

 continuity and fixity of racial or phyletic qualities, 

 weak where it attempts to explain the rhythm of 

 ontogenetic or individual development. The mnemic 

 hypothesis is at its best just where the Weismann 

 theory is weakest, that is, hi furnishing a consistent 

 explanation of the rhythm and progress of individual 

 development. Which view will triumph in the 

 end, it is impossible to predict. It is not unrea- 

 sonable to believe that the recognition of the weak 



