Vol. xxi n „ 



1905 J Jtecent Literature. 



431 



specimens, 'from time immemorial,' surely it is well known that the 

 necessity for this is due to imperfect, inaccurate and erroneous descrip- 

 tions, and not to the fact that 'perfectly "good" species' cannot be dis- 

 tinguished without comparison. If a character, whether in color, size, 

 form, texture, odor, notes, habit or anything else, cannot be detected by 

 sight, touch, smell, taste or hearing to such a degree as to admit its trans- 

 lation into intelligible language or figures, it surely is not fit to be made 

 the basis of a new name. Of course I do not contend that the ' language 

 or figures' must be intelligible to the 'layman,' for that unfortunately is 

 not at present feasible and probably never will be." 



In regard to "imperfect, inaccurate and erroneous descriptions," it may 

 be said that such we have always with us, and always will have; they 

 almost form the bulk of past descriptive zoology, and will hold also a 

 prominent place in the future; they are partly, perhaps largely, due to 

 carelessness and slovenly methods, but are in part inherent and\inavoid- 

 able, until a standard terminology for shades of difference in colors shall 

 have been invented and generally adopted. Language at present is inade- 

 quate to convey to the mind definite and exact shades of color, even 

 when strikingly different to the eye, because scarcely any two persons 

 would describe the same shades between, say buff and chestnut, running 

 through the endless tones of yellowish and reddish browns, in just the 

 same terms. Whatever the cause of this vagueness of description, it 

 exists, and will exist for a long time to come, producing a condition mili- 

 tant against Mr. Clark's 'Principle 1.' Words, as we now have to use 

 them, cannot adequately convey to the mind differences in color and 

 texture that are palpable enough when seen. 



"2. Differences in dimension*, of less than five per cent., ought not to 

 be made the basis of a new name. 



"This principle is certainly not radical, yet it would shut out a large 

 number of recently described subspecies of birds, and perhaps other ani- 

 mals also. The reason for this rule is that individual variation in a spe- 

 cies is so much larger than was formerly supposed, no constant difference 

 can be maintained between two forms which differ from each other by 

 less than five per cent, in size. I believe ten per cent, would be a safe 

 rule, but if five per cent, could be agreed on many ridiculous new names 

 would never see the light of day. In Dr. Allen's famous paper < On the 

 Mammals and Winter Birds of East Florida ' (Cambridge, 1871), he says ■ 

 'The tacts of the case show that a variation of from fifteen to twenty per 

 cent, in general size, and an equal degree of variation in the relative size 

 of different parts, may be ordinarily expected among specimens of the 

 same species and sex taken at the same locality, while in some cases the 

 variation is even greater than this.' Such being the case five per cent, is 

 not a high standard to suggest." 



While Mr. Clark's quotation from my ' Mammals and Winter Birds of 

 East Florida ' respecting individual variation is all true, there is another 

 side to the question, and that is that the average difference in general size 



