HOW SPECIES PERISH. 327 



very closely related to the Razorbill, only about the size 

 of a Goose, and with wings so small as to render it 

 incapable of flight. The Great Auk was a living though 

 a rare species not sixty years ago, now it appears to be 

 as extinct as the mammoth. The last breeding place of 

 the Great Auk was destroyed by a volcanic eruption, 

 and probably the birds perished in the general ruin. 

 All old writers on the Great Auk testified to its abun- 

 dance three hundred years ago, a period when man 

 seldom penetrated to the isolated reefs and ocean rocks 

 in the north Atlantic where the bird used to breed ; but 

 incessant and increasing persecution slowly lessened the 

 numbers of so helpless a species, and the final catastrophe 

 completed the work of extinction. The primary cause 

 of the Great Auk's extinction was its incapacity for 

 flight, its wings having gradually degenerated through a 

 long period of disuse. There can be little doubt that 

 the disuse and consequent degeneration of organs have 

 paved the way in many cases for the extinction of species 

 through the conditions of life reverting to the ones 

 prevailing when those organs were in full use and in a 

 consequently corresponding state of perfection, after a 

 long period during which they had lapsed through disuse 

 into decrepitude ; or in new conditions of life arising in 

 which those degenerated organs would have been of the 

 greatest importance to the species had their utility and 

 perfection been preserved. Had the Great Auk main- 



