126 BIRD LIFE ON ISLAND AND SHORE 
scribed, too frail to bear so tall a superstructure. 
Speculations, nevertheless, on dissimilarity between 
species on island and mainland, and on steps and 
processes likely to terminate in fixity of new 
habit, are always of special interest. At any 
rate, the altered size of the Robin’s clutch and the 
altered habits of the Bush Wren, consequent on 
proximity to the Robin, may supply hints to 
naturalists of wider comparative knowledge. Some 
ray of light may have been thrown on the genesis 
of the two-egg clutch and on the interaction of 
species crowded together through shrinkage of 
area and shrinkage of food supply. 
