ORGANIC AND INORGANIC RELATIONSHIPS 17 



Now take the case of the Guillemot. Its 

 young at birth are by no means helpless in the 

 sense that the young Reed-Eunting is, and food 

 is readily procured. But breeding stations are 

 scarce, for although there are many miles of 

 clifF-bound coast, yet not every type of rock 

 formation produces the fissures and ledges upon 

 which the bird rests. Hence vast stretches of 

 coast-line remain uninhabited, and the birds are 

 forced to concentrate at certain points, where 

 year after year they assemble in countless 

 numbers from distant parts of the ocean. If, 

 then, different individuals were to jostle one 

 another from adjoining positions, and each one 

 were to attempt to occupy a ledge in solitary 

 state, not only would the successful ones gain 

 no advantage from the additional space over 

 which they exercised dominion, but inasmuch as 

 many members that were fitted to breed would 

 be precluded from doing so, the status of the 

 species as a whole would be seriously affected. 

 The amount of space occupied by each individual 

 is therefore a matter of urgent importance. A 

 few square feet of rock sufficient for the im- 

 mediate purpose of incubation is all that can be 

 allowed if the species is to maintain its position 

 in the struggle for existence. 



Our difficulty in estimating the importance 

 of the various factors that make for success or 

 failure arises from our inability to see more than 

 a small part of the scene as it slowly unfolds 

 itself. The peculiar circumstances under which 

 these clifF-breeding forms dwell does, however. 



