268 
HYBEIDISM. 
Chap. VIII. 
common but unknown bond, wbicli is essentially related 
to the principle of life. 
Fertility of Varieties when crossed, and of their Mongrel 
offspring .—It may be urged, as a most forcible argu¬ 
ment, that there must be some essential distinction 
between species and varieties, and that there must bo 
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, we 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 
