IQ2 THE FOUNDATIONS OF ZOOLOGY 



The evidence that man has produced all the fancy breeds of 

 pigeons from a single wild species is admitted to be satisfactory ; and 

 if these fancy breeds differ among themselves as much, and under 

 continued selection keep as true to their kind as wild species, 

 it seems clear that we need not call the causes of variation to the 

 aid of natural selection to account for the origin of the various 

 species of wild pigeons from a common stock. Now the evidence 

 that these fancy breeds do thus resemble wild species, as it is 

 summarized by Darwin, in the first chapters of the " Origin/' is as 

 convincing as it is familiar, and there would be no need to refer to 

 it here, did not the strange impression prevail that selection can 

 accomplish nothing unless some other source of adaptive modifica- 

 tion furnish the raw material to be selected. 



Of domesticated pigeons Darwin says: "The diversity of the 

 breeds is something astonishing. Compare the English carrier 

 and the short-faced tumbler, and see the wonderful difference in 

 their beaks entailing corresponding differences in their skulls. 



" The carrier, more especially the male bird, is also remarkable 

 for the wonderful development of the carunculations about the 

 head; and this is accompanied by greatly elongated eyelids, very 

 large external orifices to the nostrils, and a wide gape of mouth. 

 The short-faced tumbler has a beak in outline almost like that of 

 a finch ; and the common tumbler has the singular inherited habit 

 of flying at a great height in a compact flock, and tumbling in 

 the air head over heels. 



" The runt is a bird of great size, with very long, massive beak 

 and large feet ; some of the sub-breeds of runts have very long 

 necks, others very long wings and tails, others very short tails. 

 The barb is allied to the carrier, but, instead of a long beak, has 

 a very short and broad one. The pouter has a much elongated 

 body, wings, and legs ; and its enormously developed crop, which 

 it glories in inflating, may well excite astonishment and even 

 laughter. The turbit has a short and conical beak, with a line 

 of reversed feathers down the breast ; and it has the habit of 

 continually expanding, slightly, the upper part of the oesophagus. 

 The Jacobin has the feathers so much reversed along the back 

 of the neck that they form a hood; and it has, proportionally to 

 its size, elongated wing and tail feathers. The trumpeter and 



