26 PALAEONTOLOGY OF KENTUCKY. 



larity in certain features. Inasmuch as relation between organic beings 

 depends upon their origin from common ancestors, no real relation could 

 exist outside of a species among the animals and plants, if the former belief 

 in the stability of species had remained. The erroneous views of the old school 

 were based upon observations among the more highly developed animals and 

 plants, where the division lines between the species are more pronounced. 



Had the scientists of olden times directed their investigation to the lower 

 organisms, they would soon have met with difficulties, and in many cases even 

 with impossibilities, to accomplish a specific differentiation . The evolution 

 theory has upset the views of the old school. It does not believe in a separate 

 original creation for every species, but, according to it, new ones are produced 

 by gradual modifications of old forms. Changes in organisms may be either 

 temporary, that is, dying out with the same specimen in which they first occur, 

 or they may be constant, when they reappear in all the succeeding generations. 

 Only these constant alterations will lead towards new species, and in order to 

 do this, they must intensify in every succeeding specimen, until they become 

 so characteristic as to afford an easy and sure distinction between the original 

 and the new species. It is obvious that this procedure in the creation of 

 species will leave some specimens in a doubtful position ; their modifications 

 may separate them from the old forms and still be insufficient to place them 

 among the new ones. These forms are connecting links, and serve to establish 

 a general relationship in larger groups of organism ; but they cause consider- 

 able trouble as far as classification is concerned. 



It is impossible to state the exact amount of similarity required between 

 two animals or two plants, which will place them both either in the same 

 family, the same genus, or the same species. In recent years a real mania has 

 sprung up among some naturalists to manufacture as many genera and species 

 as possible. By such proceedings science is not benefited, but only becomes 

 incumbered with synonyms, of which, sooner or later, it has to be purged. 

 Such a cleaning process will be necessary in Palaeontology. This science, 

 which has lately passed its childhood, and which handled material, the charac- 

 ter of which was little known, has certainly established species and genera 

 which will require revision. We find, for instance, of some fossil shells speci 

 mens showing the outside shell with all the markings well preserved, and 

 again, others in the condition of internal casts, with all the shell exfoliated 

 between such specimens exist differences rendering it impossible to recognize 

 their intimate relation without closer investigation. That the first geologists, 

 noticing these two different forms, described them as different species, is quite 

 natural ; but as soon as material of this kind increased, some forms were found, 

 showing partly the internal cast and partly the exterior shell, combining the 

 two fossils which were so far considered as different species. Again, we have 



