26 THE PRINCIPLES OF HEREDITY 



the acquired peculiarity be reproduced by the child. There 

 is one test, and one only, by which the transmissibility of a 

 mutilation can be proved the test of experiment, the test of 

 its constant reproduction under given conditions. Under 

 that test the hypothesis that mutilations are transmissible is 

 easily proved to be without foundation. 1 



44. Maternal impressions and telegony are supposed to 

 supply evidence, A pregnant female sees a deformity or 

 something felse which powerfully impresses her. Her child 

 when born is thought to reproduce the deformity. Thus a 

 Kerry cow chased by a bull-dog is said to have borne a calf 

 extremely like her persecutor. Telegony is a phenomenon of 

 much the same order. A mother, who has borne offspring to 

 one sire, is supposed to so influence offspring borne to subse- 

 quent sires that the latter reproduce the peculiarities of her 

 first mate ; thus a white woman who has borne a child to a 

 negro is supposed ever after to bear dark children to white 

 men ; a mare who bore a foal to a quagga is said to have borne, 

 subsequently, striped offspring to a thoroughbred horse. In 

 the one case the mother's mind is thought to be impressed ; 

 in the other her body. Both hypotheses furnish examples of 

 the amazing looseness of thought which occasionally prevails 

 in biological writing. Neither the transmission of maternal 

 impressions nor telegony has stood the test of accurate observ- 

 ation; they are popular superstitions. But suppose they 

 had been demonstrated up to the hilt ; even in that case the 

 transmission of acquirements would not have been proved ; 

 for by the transmission of acquirements we mean, or ought to 

 mean, that the precise thing the parent acquired, or something 

 very like it, is transmitted to offspring. But a mother who 

 gets a mental impression does not transmit that mental 

 impression to her child ; on the contrary, the child is supposed 

 to develop something quite different, a physical malformation. 

 So, also, did the white mother of a half-breed bear dark chil- 



1 In this, as in all similar instances, the onus of proof rests with the 

 party making the positive assertion, not with those who deny it. If 

 mutilations were transmissible the fact could easily be proved. If they 

 are not transmissible it is logically impossible to furnish formal proof 

 for the simple reason that it is impossible to prove a universal negative. 

 Thus, if a Lamarckian declared that mutilation A was transmissible and 

 his assertion were disproved, he could still declare that mutilation B was 

 transmissible ; if that also were disproved he could declare that mutila- 

 tion C was transmissible ; and so on, ad infinitum, through the entire 

 range of mutilations, actual or possible, past, present, or future. Or if 

 it were proved that a given acquirement was not transmissible in this 

 individual, the Lamarckian could declare it might be transmissible in 

 some other individual. 



