282 GENERALIZATIONS. 



in the course of time. Many other plants and animals, however, 

 completely differ from the earlier ones ; they represent sharply 

 defined types standing far away from all species known to Prof. 

 Heer ; and the bridge of transition is even wanting in the case of 

 whole classes (e. g. the birds) . Difficult as it may be to account 

 for the origin of those types in which entirely new plans of 

 structure are expressed, it seems more natural to derive them 

 from the organic than from the inorganic world. Prof. Heer 

 would have to assume that the great gaps have been produced 

 by the extinction of species which have been lost. Prof. Heer 

 therefore maintains that a genetic connexion exists through 

 the whole organic world, because it is only by this supposition 

 that he can form an idea of the origin of species, which can be 

 brought into accordance with known and intelligible natural 

 processes. 



Here, however, arises the second important question -namely, 

 whether a perfectly gradual and imperceptible transformation of 

 species, always going on without cessation, really takes place, as 

 Darwin and his adherents suppose, and which, of course, implies 

 the constant production of new forms, even at the present time. 

 This view is most decidedly contradicted by the facts which Prof. 

 Heer has already communicated ; for not only has no new species 

 originated, so far as he knows, during the period of human 

 history, but even the paper coals, which go back to a much 

 earlier time, exhibit the existing flora. 



Prof. Heer even meets with the same two varieties of the 

 hazel which now clothe the Swiss hills, and a species of snail 

 (p. 213, note) presents the same slight abnormal characteristic 

 in the structure of its shell as its descendants now living near 

 Sargans. Plants of the Swiss Alps also agree in part with those 

 of the high northern latitudes ; and these have probably issued 

 from the same centre of origin. Even in the drift period such 

 plants were moulded in exactly the same forms which they now 

 exhibit in the high mountains of Switzerland as well as in the 

 distant polar zone. 



It has been already noticed that Mr. Darwin regards the 

 mutual influence and selection of individuals as the principal 

 agents in the variations of organic nature and in the origin of 

 species ; but it is manifest that the Swiss species on the Alps live 



