NOTES. 65 



of comparison the observations recorded by Mr. William 

 Evans {Ihis, 1891, pp. 52-93, 1892, pp. 55-58) :— 



Etder Duck {Somateria mollissima). — Thirty-one days. 

 In Mr. W. Evans' experiments an egg hatched in an incubator 

 on the twenty-seventh day, and under a hen on the twenty- 

 eighth day. 



Ringed Plover {Mgialitis hiaticula). — Twenty-five days. 

 Mr. Evans' hatched in an incubator on the twenty-second, 

 twenty- third, and twenty-fifth days. 



Oyster-Catcher {Hcematopus ostralegus). — Twenty-one 

 days. Mr. Evans gives twenty-three to twenty-four days 

 from observations on two nests watched by Colonel Duthie. 



Sandwich Tern {Sterna cantiaca). — Twenty days. Not 

 given by Mr. Evans. 



Arctic Tern {S. macrura). — Twenty days. Not given by 

 Mr. Evans, but the Common Tern is given as hatching two 

 on the twenty- first, and one on the twenty-second day, in an 

 incubator. 



Herring-Gull {Larus argentatus). — Twenty-one days. Mr. 

 Evans gives the twenty-sixth day under a hen. 



Lesser Black-backed Gull {L. fuscus). — Twenty-one 

 days. Not given by Mr. Evans. 



Razorbill {Alca torda). — Twenty- five days, Mr. Evans 

 gives the thirtieth day in an incubator. Both Mr. Evans 

 and Mr. Paynter remark that they cannot be absolutely 

 certain that the eggs were fresh. 



Common Guillemot {Uria troile). — Thirty- two days. Mr. 

 Evans gives the thirtieth and thirty-third days for two eggs 

 in an incubator, and thirty-first day for one under a hen. 



Puffin {Fratercula arctica). — Thirty-six days. In this case 

 Mr. Paynter took eight eggs from different nests, and those 

 which hatched out last he took as giving the correct period. 

 Mr. Evans also gives the thirty-sixth day in an incubator. 



It will be seen that the results arrived at by Mr. Paynter 

 and Mr. Evans differ considerably in many cases. Both 

 authors took great care that the eggs used should be perfectly 

 fresh, although in cases where the bird lays only a single egg 

 this is somewhat difficult to ensure. There is no doubt con- 

 siderable individual variation, and we shall hope that other 

 ornithologists will take up the subject, so that sufficient 

 observations may be made on this interesting subject to enable 

 us to strike a reliable average of the incubation period in 

 various species. 



In the same article Mr. Paynter makes some interesting 

 remarks on the way in which Gulls, hatched in an incubator, 

 practised flying by allowing the wind to lift them a few feet, 



