THE WHITE, CHINA GOOSE. 229 



difference, that are made use of to assist in classifica- 

 tion ; but the preoise lines of demaroation of each are 

 extremely difficult to define. It is generally assumed 

 that individuals of different genera will refuse to breed 

 together ; that the mules between different species are 

 sterile ; and that varieties are merely accidental, and 

 recent instances of a slight alteration in the external 

 character of species, which do not affect their contin- 

 uance as a race, and, perhaps, disappear altogether 

 after a time. But in opposition to this, hybrids have 

 been produced between the Egyptian -goose and the 

 penguin duck, also between the common fowl and the 

 Gruinea fowl, the siskin and the Canary bird ; prolific 

 mules are constantly occurring between all sorts of 

 species of geese ; and it is well and practically known, 

 that though varieties breed freely with each other, 

 nothing is so difficult as to establish a cross that shall 

 be a perfect amalgamation of two distinct varieties. 

 Even individual peculiarities are reproduced in the 

 course of generations. For, some breeders of great 

 experience firmly maintain that white pea fowls are 

 not a mere accidental variety of the common kind, but 

 a distinct sort ; asserting that the cases, in which 

 white birds are produced from colored parents, are only 

 a breaking out of mixed blood, the " crying back,' in 

 fact, to a cross some generations past. The white 

 pea fowls are certainly of inferior size, and in their pro- 

 portions bear more resemblance to the Japan breed 

 than to the true Pavo cristatus. 



In truth, species and varieties differ only in degree. 

 If we admit that the latter are merely recent changes 

 of organization, we cannot refuse to allow that the 

 former are so likewise ; and thence proceeding back- 

 wards, we must apply the same view to genera and 

 classes, till we arrive at last at the theory of the de- 

 velopment of all animated beings from Monads, as 

 advocated by Lamarck, and more recently by the au- 

 thor of the " Vestiges of Creation," This is one mode 

 of explaining the diversity of Nature ; the other is by 



