liv INTRODUCTION. 



proach of the arctic winter, in those remarkable troops which 

 all of us have beheld cleaving the air like a wedge, often at 

 a vast height, and sometimes only recognised by their shrill 

 voices amongst the clouds. When the eggs of this species 

 are obtained, and the young are supplied with food in unli- 

 mited quantity, the result is remarkable. The intestines, 

 and with them the abdomen, become so much enlarged, that 

 the animal nearly loses the power of flight, and the powerful 

 muscles that enabled him, when in the wild state, to take 

 such flights, become feeble from disuse, and his long wings 

 are rendered unserviceable. The beautiful bird that out- 

 stripped the flight of the eagle, is now a captive without a 

 chain. A child will guide him to his resting-place with a 

 wand, and he is unable to raise himself by flight above the 

 walls of the yard that confine him ; and he gives birth to a 

 race of creatures as helpless and removed from the natural 

 condition as he himself had become. 



The Wild Duck, too, affords us a similar example. This 

 wary bird arrives in flocks from the vast morasses of the 

 colder countries. Many pairs remain in the swamps, pools, 

 and sedgy rivers, of lower latitudes ; but the greater number 

 retrace their flight to the boundless regions where they 

 themselves have been hatched, and where they can rear their 

 young in safety. If the eggs of this bird be taken, and the 

 young be supplied with food in the manner usual in the do- 

 mestic state, the animals will have changed the form, in- 

 stincts, and habits of their race. Like the Goose, they lose 

 the power of flight by the increased size of their abdomen, 

 and the diminished power of their pectoral muscles ; and 

 other parts of their body are altered to suit this conforma- 

 tion. All their habits change ; they lose the caution and 

 sense of danger which, in their native state, they possessed. 

 The male no longer retires with a single female to breed, but 

 becomes polygamous, and his progeny lose the power and 

 the will to regain the freedom of their race. The Swan, the 

 noblest of all the water-fowls, becomes chained, as it were, 



