516 MR. J. S. HUXLEY ON THE 
In birds which pair up early and remain “ married” for the 
season, hike the Grebe, one would, of course, not expect to find any 
of the regular combats seen in other species. It would be inter- 
esting to see whether there is more fighting in February, during 
the actual process of pairing-up. 
The question must now be put—‘ What for?” What is the 
good of all these divings and posturings, these actions of courtship, 
these ‘‘expressions of emotion”? ‘lo what end are colours and 
structures developed solely to be used in them, and what return 
is got for the time and energy spent in carrying them out ? 
They are common to both sexes, and so have nothing to do with 
any form of true sexual selection; they are self-exhausting pro- 
cesses, not leading up to or connected with coition, and so cannot 
be sexual excitants in the ordinary sense of the term. 
It must be, however, that they fulfil some function; and I 
believe I know what this function is. I believe that the court- 
ship ceremonies serve to keep the two birds of a pair together, 
and to keep them constant to each other. 
The Great Crested Grebe is a species in which the two sexes 
play nearly equal parts in allactivities concerned with the family. 
The cock shares equally in nest-building, -nearly eyually in in- 
cubation and early care of the young (it is only later that the 
young pass into the care of a single parent, probably the female, 
see Pycraft,’11). Thus, from the point of view of the species, 
it is obviously of importance that there should be a form of 
“marriage ””—a constancy, at least for the season—between the 
members of a pair. ‘The same result—marriage—is observable in 
such a species as man; but in man the main cause is a division of 
labour between male and female, whereas in the Grebe the sexes 
have been made as similar as possible. It would seem that the 
Grebes’ family affairs had simply required more labour to be spent 
on them, and that Evolution had happened to go along the simple 
path of increasing the quantity of labour, by bringing the male 
in to do female’s work, instead of improving the quality by 
adopting the principle of specialization. 
Birds have obviously got to a pitch where their psychological 
states play an important part in their lives. Thus, if a method is 
to be devised for keeping two birds together, provision will have 
to be made for an interplay of consciousness or emotion between 
them. It would be biologically enough if they could both quite 
blindly, and separately, attend to the common object—nest, 
eggs, or young; but with brains like theirs there is bound to be 
_a considerable amount of mental action and reaction between 
them. All birds express their feelings partly by voice, and very 
largely by motions of neck, wings, and tail; and not only this, 
but the expression can be, and is, employed as a form of language. 
This being so, we have here a basis on which can be reared various 
emotional methods of keeping birds of a pair together. As 
always, selection of accidental variations has led to very diverse 
results ; so that we see this ‘‘ emotional companionship ” playing a 
