II PERSISTEXT CHARACTERS 51 



light by Wiirteiiberger in the field of palaeontology, that 

 the last, the highest stages in the development of animals 

 govern the modification of the species. The opposite view 

 advocated by Kolliker is no more supported by facts than his 

 other propositions — it rests only on assumptions, on the con- 

 ceivable and the possible. Moreover, Kolliker, as already 

 remarked, opposes Darwinism, the utility principle, altogether.-^ 



The rest of the agencies previously mentioned as causes of 

 the division of the organic world into species will be examined 

 in subsequent sections. Here I have only to. make the 

 following preliminary remarks on 



CONSTITUTIOXAL ImPREGXATIOX 



[Constitutional Aclcvptation) 



The proposition that a character must establish itself more 

 firmly the longer it remains in an organism exposed to the 

 same conditions, in other words, the longer it is maintained by 

 continually repeated inheritance, scarcely requires any further 

 proof than is given by general physiological considerations. As 

 I have elsewhere expressed it r " If a form remains stationary 

 at a low phyletic stage, then, from purely constitutional causes, 

 the longer it remains at that stage the more does it become 

 different, because its characters stamp themselves more and 

 more deeply on the organism (constitutional impregnation). It 

 will, therefore, after a certain time no longer be the same as it 

 was when its relatives diverged from it. The longer it is able to 

 exist with these characters the more it will chano-e in another 

 way while its relatives change by correlation, but the more also 



^ Cf. Kolliker, Ueber die Darioinsche Schojifungstheorie, Zeitschr. f. tv. ZooL, 

 Bd. xiv. Also ^Morphologie tend Entioicklicngsgeschichte des Pennatuliden- 

 stammes, nehst cdlgevieinen Betrachtungen zur Descendenzlehre, Frankfurt (Sen- 

 kenbergsclie Abliandluugen), 1872. Unticicklungsgeschichte, ^ecoiidEdition, 1879, 

 pp. 6, 27. - Variiren, etc. 



