y 



1880.1 219 



the organs of flight. This may be decided by future observation. I 

 think, therefore, it is perfectly demonstrated that in the genus Salda 

 the presence or absence of raised hairs, if not conjoined with other 

 characters, is not sufficient to separate species. This observation in- 

 duces me to believe that the same thing may exist in other families, 

 and I am disposed to regard Scoloposiethus pilosics, Eeut., only as a 

 hispid variety of ;S'. ajflnis.'''' All this is at present in the region of 

 possibility or probability, scarcely " parfaitement demontre." Time 

 will show. A certain bias is given to the probability by an analogous 

 variation, often observed in plants under altered conditions ; thus De 

 Candolle, writing on the influence of climate, soil, elevation, &c., on 

 species, says, among other remarks, " If a plant accustomed to water is 

 found to live on a drier soil, it becomes covered with hairs, remains 

 smaller than usual, and acquires greater hardness." 



,y In view of the great range of variation ascertained to exist in many 

 undoubted species, and which is indeed an essential character of a 

 species, it appears very questionable if the slight differences of form, 

 size, sculpture, puncturation, or clothing, on which great numbers of 

 species have been founded, in CoJeopiera especially, will prove to be 

 real specific characters. Failing the breeding test, which must in most 

 cases happen, the best criterion of species is in the form of the genital 

 segments and their armature, but it is not always easy to determine 

 this, nor even, if ascertained, to know absolutely how far it is decisive 

 of specific difference ; yet it affords the best known means of approxi- 

 mate certainty/ 



The question of the origin of species has been intentionally 

 avoided, as not within the scope of the present paper. 



8, Beaufort Gardens, Lewisham : 

 January IMh, 1880. 



Postscript. — Since writing the foregoing I have read Froiessor 

 Huxley's new work, " The Crayfish," in which I find the following 

 aboutjpecies : — 



,/' " The word ' species ' in Biology has two significations ; the one 

 based upon morphological, the other upon physiological, considerations. 



" A species, in the strictly morphological sense, is simply an 

 assemblage of individuals which agree with one another, and differ from 

 the rest of the living world in the sum of their morphological characters ; 

 that is to say, in the structure and in the development of both sexes. 

 If the sum of these characters in one group is represented by A, and 

 that in another by ^ + «, the two are morphological species, whether 

 « represents an important or unimporiant difference. 



