538 MR. J. S. HUXLEY ON THE 
remained thus for about two minutes, then got off, apparently 
put a few bits of weed on the nest, and swam “off with the cock, 
who for his part had remained quite quiet all the time. When 
I went to inspect the nest later in the day, I found that there 
were no eggs, and that it seemed to be a mere pairing-platform— 
old, sodden, low, and covered with excreta. 
This is thus the only case on record where a bird has ascended 
the pairing-platform or nest except for the purpose of incubation 
or to go into the passive pairing-attitude. 
The cock of course uses his special platform to rest on, so it is 
possible that the pairing-platform is used by the hen as a corre- 
sponding resting-place. Or, in amplification of what I have 
already suggested (p. 518), that when the true nest is built the hen 
incubates longer and so uses that as a resting-place, the cock has 
his platform, and both sexes use the pairing-platform. 
A third possibility (but not a very likely one) is that the 
sitting on the nest (platform ) in this case was in reality only 
the first step towards assuming the passive attitude, but that the 
bird’s sexual excitement was not high enough to ‘complete the 
action. 
Most probably this, like many other bits of behaviour, was an 
“accidental” and useless release of ener ey, rendered possible by 
the mechanism of the bird’s mind. 
(iii.) Details of the Relations of Different Pairs 
to each other. 
I have thought it worth while to go into this at some length, 
in order to show how extremely complicated the birds’ mental 
states are, and how like may at a moment’s notice be turned into 
dislike. We will consider the relations of a pair with an odd 
bird in the neighbourhood. 
Let us for brevity’s sake call the three birds X, Y, and “ Y.” 
“VY” is the intruder, whom we also call the odd bird; X and Y 
are the pair, or the paired birds, cock and hen; Y is of the same 
sex as “ Y,” X of the opposite sex. This will serve when we 
want general formule. In particular cases, where the sexes 
have been accurately observed, we can employ a similar formula, 
eg. 6, 9,“9, or 6, 9, “6d,” according as the odd bird is a 
cock or hen; or we can simply say “Y”=“ 3” or “9” asithe 
case may be. 
Now for our general statements :— 
1, The disposition of X towards ““ Y” may be (a) well-disposed 
—in other words, X may be at the moment flirtatiously 
inclined in general. 
(6) Indifferent. Then X does nothing in particular, and Y 
drives “ Y” away. 
(c) Hostile. Then X helps Y drive “ Y” away ; 
but the actual initiative, the first step towards a “flirtation,” 
may be taken (1.) by X, (i1.) by ‘“ Y.” 
