CiiAr. V. ANALOGOUS VAKIATIONS. Id 



pear probable would all appear top^cthcr from simple ^•arialion. 

 More especially we might have infen-ed this, from the blue 

 color and the several marks so often appearinp^ when distinct 

 breeds of distinct colors are crossed. Hence, although under 

 Nature it must generally be left doubtful, what cases are re- 

 versions to a formerly-existing character, and what are ncAV 

 l)ut analogous variations, yet we ought, on oiu* theory, some- 

 times to iind the varying offspring of a species assuming 

 characters ((^ither from nivcrsion or from analogous variation) 

 which already are jirescnt in other members of the same group 

 and tliis undoubteclly is the case. 



A considcrabl(! jjart of the difficulty in recognizing in our 

 systematic works a variable species, is due to its varieties 

 mocking, as it were, other species of the same genus. A con- 

 siderable catalogue, also, could be given of forms intermediate 

 between two other forms, which themselves can only doubt- 

 fully be ranked as species ; and this shows, unless all these 

 forms be considered as independently-created species, that the 

 one in varjing has assumed some of the characters of the other, 

 so as to produce the intermediate forms. But the best evi- 

 dence is afforded by parts or organs of an important and gen- 

 erally uniform nature occasionally varying so as to acquire, in 

 some degree, the character of the same part or organ in an 

 allied species. I have collected a long list of such cases ; but 

 here, as before, I lie mider the great disadvantage of not being 

 able to give them. I can only repeat that such cases certainly 

 do occur, and seem to me very remarkable. 



I will, however, give one curious and complex case, not in- 

 deed as affecting any important character, but from occurring 

 in several species of the same genus, partly under domestica- 

 tion and partly under Nature. It is a case almost certainly of 

 reversion. The ass sometimes has very distinct transverse 

 bars on its legs, like those on the legs of the zebra : it has 

 been asserted that these are jilainest in the foal, and, from in- 

 qiiirics which I have made, I believe this to be true. The 

 stripe on the shoulder is sometimes double and is very variable 

 in length and outline. A white ass, but not an albino, has 

 been described without either spinal or shoulder stripe : and 

 these stripes are sometimes verv obscure, or actually (luitelost, 

 in dark-colored asses. The koulan or Pallas is said to have 

 been seen with a double shoulder-stripe. Mr. I31yth has seen 

 a specimen of the hemionus with a distinct shoulder-stripe, 

 tliough it properly has none ; and I have been informed by 



