YOUNG BIRDS AND RECORDS OF THE PAST 129 



Whilst a large number of birds have adopted this ex- 

 pedient of curtailing the activity of the young, thereby 

 increasing the burden of parental responsibility, there are 

 certain species of gaUinaceous 1- rds known as the mound- 

 builders or megapodes, which nave succeeded in reducing 

 the ties of offspring to the smallest possible limits — without 

 descending to parasitism — by enormously increasing the 

 size of the egg so as to include a proportionately large 

 amount of food-material for the growing embryo. As a 

 consequence, the whole of the normal nestling period is 

 passed within the shell, the first generation of nestling 

 down is developed and shed, and the second generation 

 together with the wing-quills are developed, before hatching 

 takes place ! 



This is a most extraordinary fact, and once more shows 

 how impossible it is to draw a hard-and-fast line between 

 embryonic and post-embryonic stages of growth. But 

 the whole history of the reproductive period of these birds 

 is strange. The parental instinct seems, in consequence 

 of this habit, to have become well-nigh extinguished, for 

 there is no brooding of the eggs, and little or no care 

 displayed for the chicks, which are hatched after the 

 fashion of many reptiles — by warmth generated by de- 

 caying vegetable matter in which the eggs are placed, or 

 in soil in the neighbourhood of hot springs. But of this 

 anon. 



That the megapodes were originally hatched in arboreal 

 nurseries, like the young hoatzin, and, as we believe, 

 all the gallinaceous birds, there can be little doubt, since 

 they also, in the nestling stage, display the free finger- 

 tip and arrested development of the outermost quills, 

 characters utterly inexplicable save on this hypothesis. 

 Further, we may feel sure that the increase in the amount 



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