518 MR. J. 8. HUXLEY ON THE 
nearly finished) next day at no great distance. In the case 
noted by Selous, during the building of each nest the cock 
built himself a platform or rudimentary nest close to the bank 
and not far from the nest that was in progress. In the con- 
struction of this the hen did not share. 
FUNCTIONS OF NEST. 
There seem to be at least three kinds of nests—the true 
nests, the pairing platforms, and the cock’s platforms. 
(1) The true nests are bulky structures, rising well out of the 
water. A single pair of birds may build more than one. In one 
of these the eggs are finally laid. It is not known whether a pair 
always build more than one (probably not), nor whether, if more 
than one is built, it is always the last that is chosen to receive 
the eggs. 
(2) The pairing platform (one seen by Selous and one by me) is 
a sodden, messy-looking structure, apparently much trodden 
down, and practically flush with the surface of the water. It 
seems to be used only as affording the necessary support for the 
action of pairing, and is apparently built some time before the 
true nest, e. g. Selous (01, p. 339 e¢ segg) watched a pair for 
three weeks and saw no nest except a single platform, which 
was used exclusively for pairing (and pairing actions). It is 
distinctly improbable (from the appearance of all true nests that 
I have examined) that such a platform would be built up and 
turned into a true nest, though no evidence on this point is 
forthcoming. 
What is certain, however, is that pairing need not always take 
place on such a platform, since Selous saw it occur ona true nest, 
and one which had probably one egg already in it. It appears to 
me likely that such platforms are built early in the season, when 
only copulation (or the preliminaries thereto), and not incubation, 
isin progress. Then, later, true nests are necessary to lay the 
eggs in, and once these are built copulation can take place in 
them just as well as on the platforms—. e. the platforms are only 
temporary expedients, rendered necessary by the birds’ pairing 
habits, and would thus phylogenetically appear to be degenerate 
nests. 
(3) The platforms of the cock. These, too, are imperfect 
structures, and are probably also degenerate nests. In the case 
observed by Selous they were built close to the bank by the cock 
alone, during the construction of a true nest close by. When 
built, they were used (by the cock alone) as resting-places where 
he sat or, more frequently, stood. 
Their true purpose is hard to see. It cannot be that the cock 
needs a resting-place more than the hen (unless—merely to state 
a case !—we suppose that in the month of May both sexes need 
