FOSSIL PEDIGREES 87 



species, working his way back, literally inch by inch, through 

 a single small group of strata. Only thus could he base on 

 the kboriously collected facts a single true interpretation; 

 and to those who preferred the broad path of generality his 

 interpretations seemed, as Bacon says they always "must 

 seem, harsh and discordant — almost like mysteries of faith." 

 . . . Thus by degrees we reject the old slippery stepping-stones 

 that so often toppled us into the stream, and, foot by foot, we 

 build a secure bridge over the waters of ignorance." {Science, 

 Sept. 17, 1920, pp. 263, 264.) 



We cannot share Bather's confidence in the security of a 

 bridge composed of even linked species. Let such a series be 

 never so perfect, let the gradation be never so minute, as it 

 might conceivably be made, when not merely distinct species, 

 but also hybrids, mutants and fluctuants are available as stop- 

 gaps, the bare fact of such intergradation tells nothing what- 

 ever concerning the problem of genetical origin and specific 

 relationship. The species-by-species method does, however, 

 represent the very minimum of requirement imposed upon the 

 palaeontologist, who professes to construct a fossil pedigree. 

 But, when all is said and done, such a method, even at its 

 best, falls considerably short of the mark. However perfectly 

 intergradent a series of fossils may be, the fact remains that 

 these petrified remnants of former life cannot be subjected 

 to breeding tests, and that, in the consequent absence of geneti- 

 cal experimentation, we have no means of determining the real 

 bearing of these facts upon the problem of interspecific re- 

 lationship. Only the somatic characters of extinct floras and 

 faunas have been conserved in the rock record of the past, and 

 even these are often rendered dubious, as we shall see pres- 

 ently, by their imperfect state of preservation. Now, it is solely 

 in conjunction with breeding experiments, that somatic char- 

 acters can give us any insight into the nature of the germinal 

 constitution of an organism, which, after all, is the cardinal 

 consideration upon which the whole question of interspecific re- 

 lationship hinges. All inferences, therefore, regarding the de- 



