WHAT IS A SPECIES? 257 



879.— Ibidorhynchus Struthersii, Vigors. 



At and near Derail there are large shingle beds where the 

 valley opens out a little. Here one or two pairs of this rare 

 and curious bird may be seen. The Crows persecute it much ; 

 and, I believe, had taken the eggs, when I was there. I made a 

 diligent search, but could not find either eggs or young. 



893.— Actitis hypoleucos, L. 



I saw a few pairs near Derali and similar places where 

 there were gravel beds. 



958.— Anas boschas, L. 



A pair were seen on a small mountain tarn above Derali. 

 The male was obtained. This was in the middle of May. 



1005. — Graculus carbo, L. 



A few seen at Barahath, perched on stones in the middle of 

 the swiftly rushing stream. 



lap is n ^cctcs ? 



To those who have neither thought nor read much on 

 subjects connected with Natural History in one or other of its 

 branches, the definition of lt species" may appear an easy 

 matter, altogether beyond controversy. 



They will say that in relation to organie life, a species is the 

 minimum admitted sub-division, one in which, with the exception 

 of differences arising from sex, age, season, malformations, and 

 similar accidental deviations from type, all the individuals 

 which compose it resemble each other in all essential points, and 

 are descended from parents, and, under natural conditions, give 

 birth to offspring, similar to themselves. 



A moment's consideration will show that this so-called defi- 

 nition only shifts the difficulty one step further. We now 

 require to define what constitutes an " essential point," and what 

 amount of difference between individuals suffices to prevent 

 their resembling each other in all essential points. A very 

 slight study, however, of scientific classification proves that 

 existing systems permit no general and precise definition of an 

 essential difference, and that differences, at any rate, of form, 

 colour, and size, that in one kingdom, order, tribe, and even 

 family, would be generally accepted as specific are as gen- 

 erally, and, as more careful investigations would show, rightly 

 so, disallowed as such in another. 



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