PKINCIPAL ATTEMPTS AT EXPLANATION 161 



their environments as those of to-day, otherwise they 

 could not have lived ; the changes in them which have 

 been observed are transformations within their type, 

 which type, as palaeontological and present observa- 

 tions show, they thoroughly retain. 



(c) Also these accidental changes, which do not go 

 beyond the particular organic type, cannot be explained 

 by natural selection. If, for instance, we accept that 

 some individual snakes become venomous ones, the 

 formation of a poison apparatus is necessary a hollow 

 or grooved lengthened tooth, a poison gland, and a 

 connection between the poison gland and the tooth. 



This apparatus would obviously only become really 

 of service to the venomous individuals concerned, 

 when for the first time it acted as such functionally; 

 previously, however, it would rather be detrimental. 

 How came it then on the assumption that the poison 

 apparatus was really gradually developed that tooth, 

 gland, and canal became harmoniously formed without 

 actual utility ? That evidently happened without the 

 aid of natural selection rather, indeed, against it : that 

 was effected by the organism itself by virtue of an 

 innate principle of purposeful striving. 



Natural selection, therefore, explains no single positive 

 acquisition which is in any way complexly formed. 1 



(d) The ' survival of the fittest/ which Darwin accepts 

 as the principle of higher development, is not proved. 



1 Compare the example which Driesch (Philos. d. Organischen, I, p. 269) 

 carried out thoroughly on Darwinian lines, viz. the acquisition of the 

 regenerative faculty in Lizards. 



M 



