ADAPTATIONS 



403 



as obtains in the fresh-water Ducks. In other words, this bulb 

 is undergoing a process of degeneration as a consequence of 

 hypertrophy. A reference to the figures below will afford a 

 better idea of these structures than a lengthy description. 



III. 44. — Types of Syrinx 



A, Mallard. B, C, Pochard. D, Goosander. E, F, Steller's Eider. G, 

 Velvet Scoter. H, I, Common Scoter (male left-hand, female right-hand figure). 



In the Mergansers this structure reaches its maximum size 

 and is supplemented by a smaller tympanum on the right side. 

 The Mergansers bring us a further complication, in the shape of 

 bulbous swellings of the middle of the windpipe. Thus in the 

 Red-breasted Merganser {Mergus serrator) the male has the 



