248 THE ZOOLOGIST. 
care in the eggs at all. And so it is with many other primitive 
birds. In the Bustard-Quails and Phalaropes, and one or two 
others, the male also does all the sitting, but this is not the 
primitive habit as developed in the Ostriches, because in the 
species I have named the female has taken on the characters of 
the male in every detail. She is larger in size, handsomer, and 
does all the courting, and she therefore assumes all the enjoy- 
ments as well as the hardships of that strange metamorphosis, 
and the male is left to sit. 
With the bird there is no deep inevitable relation between 
the female and extreme development of the parental instinct. 
Present conditions, where the female is more generally the 
maternal parent, are the results of character and difference of 
temperament in the two birds, and of relative benefits. For 
example, in a species where sexual selection had already acted, 
it would be disadvantageous for the brightly-coloured male to 
sit if the nest were on the open ground, and so the female would 
take his place. LEggs laid in holes in rotten timber—probably a 
favourite locality with primitive birds—would require assiduous 
incubation because of the lack of heat, and itis obvious that this 
warmth would be amply provided if a division of labour occurred 
among the two parents. This division of labour would prevent 
any disastrous weakening effects in the male when he is forced 
to carry out all the incubation himself. The Spotted Emu 
(Dromeus irroratus), in captivity, has been known to sit for fifty 
days, during which time it took no food, and only left the eggs 
five times. The duties of incubation are burthensome at any 
time, and the males of many species drive their females on to 
the eggs, and vice versa. 
When once incubation became necessary, it was seen that 
the female was the more suited for it. It would suit the cock- 
bird more to stand by and fight. She would be acted on by 
various physiological changes ; she would grow broody and want 
to sit of her own accord. As she grew more and more the 
sitting bird she would develop that keen sense of possession 
which would tend to create a somewhat mystic tie, as Prof. J. A. 
Thomson thinks, between the hen and hereggs. It is a fact well 
known to all that those hens which do not get broody lay more 
eggs than do those which frequently become broody. This fact 
