44 DOUBTFUL SPECIES, 



uncommon cannot be disputed. Compare the several floras 

 of Great Britain, of France, or of the United States, drawn 

 up by different botanists, and see what a surprising num- 

 ber of forms have been ranked by one botanist as good 

 Bpecies, and by another as mere varieties. Mr. H. C. 

 Watson, to whom I lie under deep obligation for assistance 

 of all kinds, has marked for me 182 British plants, which 

 are generally considered as varieties, but which have all 

 been ranked by botanists as species; and in making this 

 list he has omitted many trifling varieties, but which never- 

 theless have been ranked by some botanists as species, and 

 he has entirely omitted several highly polymorphic genera. 

 Under genera, including the most poiymorijhic forms, Mr. 

 Babington gives 251 species, whereas Mr. Bentham gives 

 only 112 — a difference of 139 doubtful forms! Among 

 animals w^hich unite for each birth, and which are highly 

 locomotive, doubtful forms, ranked by one zoologist as a 

 species and by another as a variety, can rarely be found 

 within the same country, but are common in separated 

 areas. How many of the birds and insects in North 

 America and Europe, which differ very slightly from each 

 other, have been ranked by one eminent naturalist as un- 

 doubted species, and by another as varieties, or, as they 

 are often called, geogi-aphical races ! Mr. Wallace, in 

 several valuable papers on the various animals, especially 

 on the Lepidoptera, inhabiting the islands of the great 

 Malayan Archipelago, shows that they may be classed under 

 four heads, namely, as variable forms, as local forms, as 

 geographical races or sub-species, and as true representa- 

 tive species. The first or variable forms vary much within 

 the limits of the same island. The local forms are moder- 

 ately constant and distinct in each separate island; but 

 when all from the several islands are compared together, 

 the differences are seen to be so slight and graduated that 

 it is impossible to define or describe them, though at the 

 same time the extreme forms are sufficiently distinct. 

 The geographical races or sub-species are local forms 

 completely fixed and isolated ; but as they do not 

 differ from each other by strongly marked and 

 important characters, ** There is no possible test but 

 individual opinion to determine which of them shall be 

 considered as species and which as varieties."" Lastly, 



