Vol. XXXV.] 84 



Trocholapteron simile and lineatum, both absolutely similar 

 structurally, absolutely different in colour and pattern, the 

 same occurs again in our Spotted and Pied Flycatchers and 

 in the genus Pm-us and many others. Of course, the whole 

 question turns on what constitutes a genus, as several have 

 already remarked. Those who favour colour as a generic 

 factor would no doubt separate the Yellow Wagtails from 

 the Pied Wagtails, those who do not would unite them as 

 Motacilla, but I certainly think tliat they have hit on a very 

 fortunate example for colour-factor in the ^gialitis group, 

 in which there is much more to be said for colour-pattern 

 and coloration than in a great many. 



Mr. Grant, I think, mentioned that Ave should look to 

 anatomy for family differentiation : this is, I think, true, 

 provided we look at the subject widely and with common- 

 sense, and do not go on peculiarities of one system ; though 

 if studied carefully the latter, I think, might possibly help 

 us in generic differentiation. 



The Chaikman : I think we ought to be very grateful to 

 Dr. Lowe for the amount of trouble he has taken to get 

 up this subject, which is of very great interest. As he 

 referred so pointedly to the questions of the Galapagos 

 Finches, I should like to say that Dr. Hartert and I tried 

 to come to a similar conclusion at one time as to the much 

 smaller number of species existing than were supposed to 

 exist. We were, however, unable to definitely state this as 

 a fact, and I do not think anyone looking at it from our 

 point of view could possibly " lump " these Finches into 

 only a few species. At the present state of evolution the 

 series on the different islands is very differently constituted, 

 on one island one link has disappeared, while on the next 

 island probably a different link in the series is lost, so that, 

 even from the large material which we have been able to 

 gather together at Tring and in the British Museum, it is 

 impossible to say definitely that one or more of these forms 

 constitute a subspecies of any given species. The only 

 thing we were able to do was to take the size and shape of 

 a bill as nearly as possible equivalent, on each island where 



