15 [Vol. xxxvi. 



suborders or, more usually, for each " Tribus^^ and " Familie/^ 

 Evidently, therefore, he values them chiefly for generic or 

 family distinctions rather than for the main divisions. Yet 

 it is surprising to find how frequently common characteristics 

 are found throughout a whole order in more recent schemes 

 of classification. 



From 1860 up to the present time little has been written 

 on the subject. Dr. Kutter's early death prevented him 

 from giving us more than a couple of interesting papers in 

 the ' Journal fiir Ornithologie ' (1877-78) and another in 

 1889 *. Dr. Hartert also addressed the Senckenberg Society 

 at Frankfort on the same subject in 1890, but this paper 

 I have been unable to see. In 1905 the late Dr. E. Rey 

 published a work on the eggs of mid-European birds f, 

 classified according to oological characters. A very notice- 

 able point about this work is that he does not confine himself 

 to the egg as Des Murs did, but utilizes nesting-sites, 

 number of eggs in the clutch, and even nesting materials as 

 characteristics. Without going so far as this, except as 

 forming a rough key for practical use, I think that he 

 indicates a weak spot in Des Murs's work. The number of 

 eggs in the clutch of any species varies within certain limits, 

 but the consistency with which every known bird in the 

 order Procellariiformes lays only a single egg, while most of 

 the Columbse, Caprimulgidse, and all the Colymbidse lay 

 normally two, and the Larid*, as a rule, lay three (with the 

 exception of the Stercorariidse, which only lay two), the 

 Limicolae rising to three and in most cases four, the Passeres 

 generally four or five to six, and the Galliformes generally 

 still more, indicates that here is a most valuable character 

 which has been much neglected. As Dr. Rey confined his 

 scheme to European birds, he avoided many of the problems 

 which face the student of the wider subject. To these we 

 will return later. 



Aud now as to the eggs themselves. When we come to 

 consider that the shell is merely a temporary protective 

 covering of calcium carbonate, necessarily formed in a 



* "■ Ueber d. wissenscliaftl. Bedeutung der Oologie." 

 t ' Die Eier d. Vogel Mittel-Europas.' 



