210 TRANSMISSION OF ACQUIRED CHARACTERS 



be in man, as there was in the ancestors of the modern horse, a 

 constitutional variation in the direction of reducing digits ; 

 and there are other possible explanations of the rather vague 

 assertions. It need hardly be pointed out that unless there is 

 a measurably progressive dwindling with similar boots in the 

 course of generations the case has no point. A control experi- 

 ment comparing the toes in sets of brothers respectively booted 

 and bootless would be interesting. 



Results of Pressure. Darwin (Descent of Man, p. 18) regards 

 the thickened sole of even unborn infants as due to " the in- 

 herited effects of pressure during a long series of generations." 

 But here again it is impossible to exclude the interpretation that 

 a variation in the direction of thickened solar epidermis might 

 have selection- value from very ancient days, to the arboreal 

 ape as well as to the bootless man. H. H. Wilder, in a paper 

 in which he gives a detailed comparison of the palms and soles 

 of Primates and Man (Anat. Anzeig. xiii. (1897), pp. 250-6), 

 distinctly refuses to commit himself to a Lamarckian theory, 

 believing that the facts may be equally well interpreted in 

 terms of variation and selection. 



Bollinger (1882) suggests that the weak development of the 

 breasts in women of the Dachauer district is due to the old- 

 established fashion of wearing tight corsets which are pressed flat 

 on the breasts. It is necessary to inquire (a) whether the pecu- 

 liarity is not a modification inflicted on each successive generation, 

 or whether it is ever exhibited by a Dachauer woman who does 

 not wear a corset ; and (b) whether the same peculiarity does 

 not occur where the fashion is entirely different. 



Climatic Changes. Virchow and others have laid stress on 

 the fact that many peculiarities in races of men and of other 

 living creatures are climatic in origin, and yet are now part of 

 the natural inheritance. But acclimatisation is usually a slow 

 and gradual process, involving selection of germinal variations, 

 and it is difficult to get clear-cut cases of climatic modifications. 



