No. 643] 



ORTHOGENESIS 



139 



mentary species a "Mutation" of Waagen is compa- 

 rable to a "Mutant" of De Vries in external appearance, 

 but not in mode of origin, because one arises through a 

 continuous " Mutationsrichtung/' while the other arises 

 through accidental germinal saltation. To my mind the 

 continuous or discontinuous mode of origin either of a 

 "mutation" or of a "mutant" is of small account as 

 compared with the fortuitous or orthogenetic nature of 

 the impulse in the germplasm which gives rise to it.^ 



So far as I know all observers of the hard parts of 

 extinct animals, whether vertebrate or invertebrate, con- 

 firm this classic observation of Waagen, and many in 

 this special field of observation also confirm the "Mtita- 

 iionsriclitmuj" of Neumayr. So far as I personally 

 have observed, this principle of "Mutationsrichtung" 

 is especially dominant in the origins of characters; here 

 at least other interpretations are not applicable; there 

 is no question of Selection between two alternatives, 

 adaptive and inadaptive, because the inadaptive does 

 not occur, the whole process is adaptive and the differ- 

 ence between two organisms is the ra[)idity and direc- 

 tion with which the Miitatiousyichiwjfj'' is acting. 

 This is the same in the hard parts of the molluscs .1)^/- 

 wonites, Pahid'wa, and Planorhis, as it is in the mam- 

 mals Equus, Bh 'moceros, and Elephas. 



3. The Ortgix of New Propoktioxs 

 In the evolution of proportions, that is, proportions 

 in the different parts of skeleton and skull as in Spheno- 

 don, Drinodou, Stnithiomlmus, Diatri/ma, it appears 

 probable that Selection may be constantly working on 

 all adaptive fluctuations of proportion in connection 

 with oiitoo'enetic modifications in proportion which are 

 alM. ;ulai)tivr. a< in tli<' classic case cited by Imtli Dar- 

 ^K]u nud L.-unnivk of th. h-uutl! of ih. n.rk of tlu^ -iraffe. 



