522 MB. J. S. HUXLEY ON THE 
the initiative in flirtation, although from my records the cock 
seems to do so rather oftener than the hen. 
Where there is a simple pleasurable ceremony, for whose 
performance two birds are necessary, it would seem quite natural 
that flirtation would occur. If the ceremony is an advantageous 
one, flirtation represents an overshooting of the mark by Natural 
Selection—a slight disharmony. ‘‘ Adultery” I would think very 
improbable in this species, since the act of pairing is connected 
with a nest, built jointly by the pair, in a definite spot of their 
own territory. 
(v.) Other Activities. 
Incubation. 
It appears that both sexes sit, but that probably the hen sits for 
a much longer time. Mr. A.'T. A. Ritchie informs me that when 
there is a punt near the nest and the hen does not want to return 
to the eggs, the cock will often drive her to her duties. 
Care of the Young. 
After the young birds are hatched, both parents attend on 
them for some time; but later in the season, when the young are 
half-grown, the observations of Mr. W. P. Pycraft (Pyeraft, °11) 
make it certain that only a single bird, probably the hen, looks 
after the brood. 
Thus here there is no complete and qualitative division between 
the sexes, except in this last particular. 
There is, however, rather more of a quantitative division than 
usual. 
6. Discussion. 
There are various considerable difficulties concerned with the 
courtship-structures and actions of the Great Crested Grebe. 
In the first place, it is clear, from what has been said, that in this 
bird there is no sexual selection in the ordinary sense of the 
word ; the crest and the courtship-actions are almost identically 
developed in cock and hen alike. 
On the other hand, the crest is only fully developed in the 
breeding-season, thus resembling true secondary sexual characters; 
and, as I have pointed out (Huxley, ’12,) it is used only in 
courtship, so that if not “secondary,” it is at least “sexual.” 
Further, the crest is smaller (though but slightly) in the 
female than in the male, a fact which it is, at first sight, simplest 
to explain by assuming that the crest was acquired by the cock 
as a secondary sexual character, and has now been almost com- 
pletely transferred to the hen (cf. similar transference, complete 
or incomplete, in Lycenid and other butterflies (Weismann), 
Reindeer, mammz of mammals, colours of many birds). We 
will revert to this point. 
