268 HYBRIDISM. Chap. VIII. 



ment, that there must be some essential distinction 

 between species and varieties, and that there must be 

 some error in all the foregoing remarks, inasmuch as 

 varieties, however much they may differ from each 

 other in external appearance, cross with perfect facility, 

 and yield perfectly fertile offspring. I fully admit that 

 this is almost invariably the case. But if we look to 

 varieties produced under nature, we are immediately 

 involved in hopeless difficulties ; for if two hitherto 

 reputed varieties be found in any degree sterile to- 

 gether, they are at once ranked by most naturalists 

 as species. For instance, the blue and red pimpernel, 

 the primrose and cowslip, which are considered by 

 many of our best botanists as varieties, are said by 

 Gartner not to be quite fertile when crossed, and he 

 consequently ranks them as undoubted species. If we 

 thus argue in a circle, the fertility of all varieties pro- 

 duced under nature will assuredly have to be granted. 



If we turn to varieties, produced, or supposed to have 

 been produced, under domestication, v^e are still in- 

 volved in doubt. For when it is stated, for instance, 

 that the German Spitz dog unites more easily than 

 other dogs with foxes, or that certain South American 

 indigenous domestic dogs do not readily cross with Euro- 

 pean dogs, the explanation which will occur to every 

 one, and probably the true one, is that these dogs have 

 descended from several aboriginally distinct species. 

 Nevertheless the perfect fertility of so many domestic 

 varieties, differing widely from each other in appear- 

 ance, for instance of the pigeon or of the cabbage, is 

 a remarkable fact ; more especially when we reflect 

 how many species there are, which, though resem- 

 bling each other most closely, are utterly sterile when 

 intercrossed. Several considerations, however, render 

 the fertility of domestic varieties less remarkable than 



