i6o Danaiii and Romanes dealt witJi. 



XXI. 



With regard to the second half of the passage from 

 Mr. Darwin's Origin of Species, it really, while pro- 

 fessing wholly to solve the problem, practically leaves 

 it untouched. The difficulty most closely presses on 

 this very point which Mr. Darwin slips over in the 

 lightest possible manner ; not deigning at all to deal 

 with it. And the question is this : whether, result- 

 ing from definitely traceable changed external cir- 

 cumstances, or from slightly modified function, or 

 both acting together or reacting on each other — the 

 American cuckoos do now, as Mr. Darwin presumes 

 the ancient progenitor of our European cuckoo did, 

 occasionally lay an egg in another bird's nest. No 

 help is gained by saying that other birds occasionally 

 — (as in the case of pheasants laying in partridges' 

 nests, etc.) — lay eggs in other birds' nests, because in 

 none of these cases do we have any marked or even 

 noticeable tendency to any progress whatever in the 

 same direction as the European cuckoos have, on his 

 theory, taken. The analogy, therefore, completely 

 breaks down at the point where it should be strongest, 

 and is, in fact, no analogy at all. The most marked 

 point about our cuckoos is the smallness of the eggs. 

 The non-parasitic American cuckoos, as he somewhat 

 maladroitly tells, lay full-sized eggs ; but if they 

 have for ages occasionally laid eggs in other birds' 

 nests, and are moving on the way to fixed habit in 

 this respect, the eggs should already be a trifie less 

 than full sized. 



And this point does not receive the attention we 



