146 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



danicus, comitatensis, bollenensis, ruscinensis, pyren- 

 aicus, perpinianus, etc., which indicate their geo- 

 graphical origin. " The only constant difference 

 in the sub-Apennine species is the size, generally 

 smaller in the basin of the Rhone, a difference 

 which is only noticeable towards the end of the 

 gulf to the north of Avignon. . . . Most of these 

 varieties correspond to regional varieties, and 

 would be considered as real species by sectionists 

 a outrance." The localization of these races in the 

 basin of the Rhone is easily explained, moreover, 

 by the obstacle which the existence of a long 

 Corsican and Sardinian peninsula united to Pro- 

 vence must have raised against the communication 

 of Molluscs of the Rhodanian gulf with those of 

 the Ligurian shore or of Tuscany. 



These interesting facts concerning the localization 

 of regional races at the various geological epochs 

 would appear with still more frequency if palae- 

 ontologists had not acquired the deplorable habit 

 of designating these races by distinct specific names, 

 which have had the consequence of breaking the 

 natural links uniting the different forms of the 

 same group. 



Taking altogether the facts set forth above, it 

 follows that the variability of species was the same 

 in early times as in the present epoch. This 

 variability shows itself by a polymorphism at times 

 almost null, and at others intense among certain 

 species. The result is the creation of groups of 

 forms, among which we ought to make a distinction 

 between varieties produced everywhere and without 

 apparent reason round some specific central type, 



