218 Descriptive Zoology. 



smell, yet experiment seems to show that this is not so 

 acute as supposed. 



The Pigeon's Voice. The cooing of the pigeon is pro- 

 duced by air vibrations made in the windpipe, but not, as 

 in most animals with a true voice, in a larynx at the upper 

 part of the windpipe. In birds the organ of the voice is at 

 the lower end of the windpipe, where it forks to form the 

 two bronchi ; and it is called a syrinx instead of a larynx. 

 The bird uses the voice to utter cries of warning, to call 

 the young, and to attract attention in the mating season. 

 It is worthy of notice that the sweetest singers are not to 

 be found among the highly colored birds, but among those 

 of more subdued tints. 



Origin of the Domesticated Pigeon. All other varieties 

 of domesticated pigeons appear to have descended from 

 the rock pigeon of the old world. By carefully selecting 

 pigeons having certain peculiarities, and breeding from 

 these to the exclusion of other forms, in time we have 

 produced a large number of varieties of pigeons, known as 

 carriers, pouters, fantails, etc. This production of vari- 

 eties by interfering with the natural selection of mates is 

 known as artificial selection. 



A Bird's Egg. Birds' eggs are proportionately larg( 

 This might naturally be expected, since there is depositec 

 within the egg sufficient nourishment to form the chick in 

 resemblance to the adult. The eggs are formed in tl 

 ovary, and it is interesting to find that but one ovary (th( 

 left) is developed, though the right ovary is represented by 

 a rudiment. The eggs as produced by the ovary consist 

 simply of the yolk. On one side of the yolk is the germ 

 spot. As the yolk, which is the real egg, passes along the 

 oviduct, it has added to it first an enveloping mass of 

 transparent substance which is termed the " white of th< 



