Mutating Species 
Java, and Bicheno’s Finch (S. dechenovii) of 
Australia, only differ in the former having the 
rump black, while in the latter it is white, and 
this difference appears to be of the nature of a 
mutation. 
So, it might be urged, is the pure white breast 
of the male Upland Goose (Chloéphaga magel- 
fanica), which part, in the very similar C. dispar, 
is barred as in the females, the latter form being 
probably the ancestor. 
The differences between the silver-grey-necked 
Crowned Crane of the Cape (Bakarica chryso- 
pelargus) and the dark-necked species of West 
Africa (B. regulorum) seem also to be not more 
than could be accounted for by mutation. 
Peculiar forms, such as a rabbit with a con- 
voluted brain or a mouse with a peculiar pattern 
of molar teeth, have been come upon by 
anatomists. 
The above-cited mutations are all very con- 
siderable ones, and we do not profess to have 
mentioned a tenth part of those which have 
actually been recorded. 
We trust that we have collected and set forth 
sufficient evidence to show that the phenomenon 
of discontinuous variation is a very general one, 
and this would seem to tell against the hypo- 
thesis of De Vries that species pass through 
alternate periods of comparative stability and 
periods when swarms of mutations appear. We 
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