8o 



of armour exactly corresponding to the plates on the armadillo, 

 but greatly larger in size, shewing at the same time the close rela- 

 tion and yet the difference between existing forms and those of a 

 past age. The question then arose, whether variation to such an 

 extent was possible, and how such variation might arise. His great 

 work, " Animals and Plants under Domestication," reveals to us 

 to some extent his labours to obtain a solution of this problem. 

 To few men is given the patience, the fixity of purpose, the love 

 of truth, which that work displays — or rather which that work 

 records ; for the book itself gives us only a faint idea of the 

 thought and the labour involved in all the experiments and inves- 

 tigations which he carried on. He has amply demonstrated that 

 variations occur in nature both in plants and animals. That man 

 by a course of selection can accumulate these variations, till they 

 amount to an extent of divergence that would be considered more 

 than sufficient to establish distinct species, it the results merely 

 were put before a competent naturalist, who did not know their 

 history. Morphologically they are distinct, and the induced va- 

 riation is often far greater than would be considered necessary to 

 constitute distinct species, but they are fertile with each other, 

 distinct species are said not to be so. Mr. Darwin, in his most 

 interesting chapters on hybridism, crossing, &c, has shown that 

 the degrees of sterility vary exceedingly. Some species are fertile 

 when crossed ; some distinct genera are even so. Infertility pre- 

 sents a graduated scale, often quite different, when with the same 

 two species the sexes are changed. 



Our domestic breeds of the cow, sheep, and dog, are either the 

 products of distinct species, in which case distinct species have 

 been fertile, or they are the descendants of one species, in which 

 case variation has advanced to the limits of the specific, for morpho- 

 logically they differ greatly. The differences produced in the de- 

 scendants of the rock pigeon are so great, that they exceed those 

 which separate the most distinct natural genera. The domes- 

 tic rabbit differs from the wild immensely in size, in the bones 

 of the head, jaws, and vertebrae. In 141 8, I. Gonzales Zarco 

 turned out from his ship on the island of Porto Santo, one of 



