28 THE NATURALIST'S GUIDE. 



these gently with the point of the knife, and beneath them 

 will be seen the sexual organs, which are fully illustrated 

 in the following diagrams. 



Plate V., Fig. 2, is an adult male ($) in the breeding 

 season. 1 shows the position of the lungs, 2 the pecu- 

 liar yellowish glands, — in some birds bright yellow, in the 

 present case — that of a song sparrow (Melospiza melodia, 

 Baird) — they are yellowish white, which, being present 

 in both sexes, if not examined closely, may be easily mis- 

 taken, in the young female, for the testicles of the male. 

 3, 3, are the testicles, much enlarged in this, the breeding 

 season. The sex of a bird in this stage is easily deter- 

 mined. 



Plate VI., Fig. 1, is a young male ($) in the young- 

 of-the-year plumage. The figures refer to the same parts 

 as explained in the preceding. It will be perceived that 

 the testicles (3) are much smaller. At different seasons, 

 the testicles vary in size between this and the preceding. 

 In some birds they are elongated, and black in color, 

 as in the Herons ; but they always occupy the same posi- 

 tions so nearly as to be readily distinguished. The pecu- 

 liar white glands (2) are in this instance very prominent, 

 but they are readily known in all birds by their being flat, 

 while the testicles are always spherical. 



Plate V, Fig. 1. This is an adult female (?) in the 

 breeding season. 1, 1, are the same peculiar glands observed 

 in the males; 2 is the ovary, a mass of spheres at this 

 season quite yellow and prominent; 3 is the oviduct, or 

 egg-passage, much enlarged in the present case, as it always 

 is during the breeding season, when it assumes a thick, 

 swollen appearance, while at other times it is translucent, 

 much smaller, and resembles a narrow, whitish line, not 

 readily perceived. 



Plate VI., Fig. 2, is a young-of-the-year female in au- 

 tumn. 1,1, the same white glands that at this stage of the 



