RECENT CRITICISMS AND HYPOTHESES. 663 



dominantly in the direction of decrease, it can only be by 

 silently assuming tlie cause which is overtly denied. 



But now we come to the strange fact that the particular 

 case in which panmixia is assigned in disproof of alleged 

 inheritance of functionally-produced modifications, is a case 

 in which it would be inapplicable even were its assumption 

 legitimate — the case of disused organs in domestic animals. 

 For since nutrition is here abundant, the principle of economy 

 under the form alleged does not come into play. Contrari- 

 wise, there even occurs a partial re-development of rudi- 

 mentary organs: instances named by Mr. Darwin being the 

 supplementary mammae in cows, fifth toes on the hind feet 

 of dogs, spurs and comb in hens, and canine teeth in mares. 

 Now clearly, if organs disused for innumerable generations 

 may thus vary in the direction of increase, it must, a fortiori, 

 be so with recently disused organs, and there disappears all 

 plea (even the illegitimate plea) for assuming that in the 

 wing of a wild duck which has become domesticated, the minus 

 variations will exceed the plus variations: the hypothesis of 

 panmixia loses its postulate. 



If it be said that Mr, Darwin's argument is based on the 

 changed ratio between the weights of leg-bones and wing- 

 bones, and that this changed ratio may result not from de- 

 crease of the wing-bones but from increase of the leg-bones, 

 then there comes a fatal reply. Such increase cannot be 

 ascribed to selection of varieties, since there is no selec- 

 tive breeding to obtain larger legs, and as it is not pretended 

 that panmixia accounts for increase the case is lost : there 

 remains no cause for such increase save increase of function. 



§ 174c. The doctrine of determinate evolution or definitely- 

 directed evolution, which appears to be in one form or other 

 entertained by sundry naturalists, has been set forth by the 

 late Prof. Eimer under the title " Orthogenesis." A distinct 

 statement of his conception is not easily made for the reason 

 that, as I think, the conception itself is indistinct. Here are 

 Bome extracts from a translation of his paper published at 



