HENS WITH ONE CHICKEN 149 



sooner or later at the attempted laying of her first 

 egg, the egg not being reduced proportionately 

 to the size of the hen. Sonaething of this sort may 

 have operated to prevent Humming-birds becoming 

 as small as blue-bottles — the actually smallest 

 species, .Calypte helence of Cuba, being just about 

 as big as a queen humble-bee, though I doubt if 

 it is as light as Mellisuga minima, which used, as its 

 name implies, to be considered the smallest of birds. 



The Storm-Petrel, smallest of web-footed fowl, 

 certainly lays a very large egg for its size, although 

 the young is helpless ; it is not. larger than a Swal- 

 low, while its egg measures an inch in length, and 

 this is not purely a matter of disproportion to 

 reduced size, for Petrels generally lay a large egg. 



It is worth noticing that it is among birds which 

 lay a single egg that the most sensationally numerous 

 species are found ; the Passenger Pigeon of America 

 (Ectofistes migratorius), so recently eztinct, whose 

 columns used to take hours to pass a given spot, 

 was one of the Pigeons which lay but one egg. The 

 Puffin is supposed by some to be the most numerous 

 bird in Europe, and some of its brother Auks, like 

 the Guillemot, are also inordinately numerous ; the 

 extinct Great Auk was wonderfully abundant in its 

 day, as is the common Gannet still for a bird of 

 its size, while according to Darwin, the Fulmar 

 Petrel is said to be the most numerous bird in the 

 world. This is very doubtful, but he might have 

 been thinking of another Petrel, the Mutton-bird 

 {Puffinus brevicauda), which has been seen in enor- 



