338 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1921. 



animals and among human families are simple coincidences, which 

 have no more interest and often no more authenticity than cases of 

 supposed maternal impressions. The experiments of Brown-Sequard, 

 badly done moreover, which concern the heredity of mutilations and 

 that of physiological disorders following nervous mutilations, have 

 been completely disproved by researches which inspire confidence, 

 and there is nothing left of them. 



Various authors have affirmed the heredity of acquired characters 

 of the fifth category, as little likely as this seems. Here are some ex- 

 amples which Hachet-Souplet reports as demonstrative. 4 A macaque 

 monkey which he had taught, not without difficulty, to kill rats, 

 gave birth to young who hunted rats marvelously; cats trained to 

 respect mice had young which did not take mice, even when the 

 distribution of their food was intentionally retarded; sparrows 

 trained to draw a chain from a little well for six generations gave 

 birth to young which, without training, were able to draw the same 

 chain. A dog had been trained to make rapid pirouettes to the left; 

 a daughter of this dog, raised in the country, having no example 

 before her eyes and having received no training, began by herself 

 to make pirouettes to the left toward five or six months of age. All 

 that is very astonishing. Although one can not criticize experiments 

 which he has not followed, I am persuaded that there is a " hole " in 

 these observations, due perhaps to the deceit of assistants, to a 

 surreptitious training continued unobserved, etc., and I do not doubt 

 that the heredity of acquisitions of training will go to join that of 

 mutilations. 



The third category concerns the factors of the medium; no one 

 doubts their determining influence on the characters of animals and 

 plants, and it is certain that when they have been made to vary ex- 

 perimentally up to the extreme limits compatible with life there often 

 result notable modifications among beings which are submitted from 

 youth to a change of environment. But the question is to know 

 whether these modifications pass, even in a very attenuated degree, 

 to the succeeding generation reared in the normal medium. If they 

 do, we have the key to the formation of geographical races and of 

 many adaptations; for it is a fact that the results of the action of 

 the medium would necessarily be cumulative, and after a sufficient 

 number of generations passed in the modifying medium, the species 

 might be very notably transformed, perhaps even irreversibly; if 

 they do not, the effects of the medium would be produced anew for 

 each individual, without cumulation, and the influence of the environ- 

 ment on the body would no longer have any interest from the point 



* Hachet-Souplet, La gcnese des instincts, etude experimentale, Bibliotheque de Philos. 

 sclent., Flammarion, Paris, 1912. P. 239. 



