ACQUIRED CHARACTERS IN ANIMAL BREEDING 483 



gists, but in a more refined form. Semon, for example, has proposed the 

 " Mnemetheorie " as founded upon two premises. First, that although 

 the stimulations of the "sensitive substance of the organism" disappear 

 as such, yet after they cease they leave behind in this same sensitive 

 substance changes which he has called Engramme. Second, that these 

 "Engramme in the sensitive substance" persist not only in the soma, but 

 also under favorable circumstances in the germ cells. This form of the 

 "memory theory " of heredity might seem to be a convenient hypothesis for 

 explaining the assumed inheritance of modifications resulting from the use 

 of organs, but it is difficult to imagine how it would favor the assumption 

 of inheritance of modifications resulting from disuse of organs or loss of 

 parts through mutilation. Obviously the inheritance of mutilations, in 

 spite of a few circumstantial cases, cannot be maintained with any 

 degree of conviction. The many generations through which circumcision 

 has been practised in the Jew and the deforming of women's feet by the 

 Chinese are two instances opposed to it. Dehorning of cattle, docking 

 the tails of horses and sheep, clipping the ears of dogs, are instances 

 which come within agricultural practice and have no permanent effect 

 upon the breed. On the whole the neo-Lamarckians have come to 

 believe, therefore, in the inheritance of those acquired characters which 

 depend upon use or disuse of organs, achieved characters as distinguished 

 from thrust characters. A rather crude example of this belief which has 

 of late years obtained some notoriety among livestock breeders is Red- 

 field's theory of dynamic evolution. According to this statement of the 

 belief, the exercise of any organ or function results in a corresponding 

 storage of energy in the germ cells, such that the effects are transmitted 

 to the next generation. The idea receives practical application from the 

 further consequence, that this storage of energy having been granted, 

 developed animals must of necessity possess more of it than those un- 

 developed, and consequently such animals produce superior offspring. 

 E. Davenport, Marshall, Pearl and others have taken issue with Redfield 

 upon this subject and have demonstrated clearly that the facts which 

 have been cited in support of his theory of dynamic evolution may be 

 interpreted with far greater probability in other ways. In fact, the 

 biological basis for such assumption as the storage of energy in germ cells 

 is very slight. Moreover, the theory is evidently based upon a naive 

 disregard of known biological facts, and a non-critical interpretation of 

 statistical data. The matter deserves mention here, not because of any 

 merit in it, but solely because of the publicity which has been accorded 

 it in various journals devoted to practical breeding interests. 



As an example of the kind of agricultural data which those who 

 believe in the inheritance of acquired characters point to for support 

 of their views, nothing is more striking than the rise and improvement of 



