G40 Letters, Extracts, and Notes. 



definition which would cover all cases, aud that for tlie A'ery 

 simple reason that '^ species'^ is merely a very convenient 

 term founded by systematists to enable us to arrange and 

 classify animal and plant life, but it is not a natural 

 division. Some forms are so far differentiated that it is 

 easy to call them different species ; others are in process of 

 differentiation, and to recognise these we fall back on the 

 term " subspecies." Others, again, as in the case of these 

 Wheatears, are perhaps evolving by what is known as 

 discontinuous variation, and oar system has no recognised 

 means of dealing with it. 



If we go down to derivations we find that the word 

 " species " in the zoological sense is probably cognate to 

 the old word, which referred to " money paid by the tale,'' 

 and we read in Skeat that this was " probably by confusion 

 with the Latin al)lative specie, as if paid in specie = equals 

 paid in visible coin." (Tlie italics are mine.) We have 

 therefore considerable evidence to show that " species " 

 referred to forms that were visibly different, as for example 

 in the case of these two Wheatears, 



Dr. Hartert has not given us any instance of these two 

 forms interbreeding, and I doubt if any evidence exists 

 as yet, for it would be necessary to take the young alive 

 from various nests of which the parents were known and 

 see if both forms of male were found in the same nest 

 and the proportions of each form ; Avhen this has been done 

 Ave shall be in a better position to understand the true 

 meanings of these forms, and a steady advance in our know- 

 ledge will have been made. Till then there may be much to 

 be said on both sides, but nothing that can prevent it 

 remaining a matter of convenience and opinion. 



I am. Sir, 



Yours faithfully, 



J. Lewis Bonhote. 

 Government Zoological Gardens, Giza, 

 Nr. Cairo, Egypt. 



May 27, ]9iri. 



