5IL MR. J. §S. HUXLEY ON THE 
of excitement and enjoyment, seemingly as thrilling to the birds 
as it is to the watcher, but, like all the other courtship-actions, 
self-exhausting. 3 : 
Very interesting “‘incomplete stages In development of this 
ceremony were seen in one pair of birds, ranging from simple 
diving to the complete ceremony (see below). 
(e) Other Courtship Ceremonies. 
(1) Back-to-back Ceremony. 
There are considerable individual variations in the courtship- 
activities of the Grebe, and I have seen occurrences which may 
well be interpreted as rudiments of new ceremonies. In one pair, 
for instance (section 10, record 12), the birds almost always went 
into a formal back to back, or rather tail to tail, attitude after 
each bout of shaking. 
(2) Diving Ceremony. 
Other actions seem to stand in some relation to the more highly- 
developed ceremonies. For instance (pp. 545, 552), simple diving, 
either by one or both birds, without any fetching of weed from 
the bottom, is introduced as part of the courtship between the 
two bouts of shaking. 
(3) Weed-trick Ceremony. 
In still other cases, the weed-trick is gone through and is 
followed immediately by a bout of shaking. In both pairs in 
which this was seen, one bird alone brought weed, although in 
one pair (not in the other) both had previously dived. I am 
inclined to believe (but more observations are needed) that two 
(distinct ceremonies are here involved: first, the fetching and 
offering of weed by one bird, usually the cock, to its mate; and, 
secondly, a typically “mutual” ceremony involving simultaneous 
diving of both birds of a pair: and on to this latter the “ penguin 
dance” has been grafted. 
The offering of weed is strongly reminiscent of occurrences in 
the sex-differentiated, non-mutual courtships of other birds, such 
as the Warblers, where the cock often carries Jeaves or twigs 
in his mouth during sexual ecstasy (Howard). It seems to me 
probable that, since diving is necessary for weed-fetching, the one 
has come to be associated with the other, and the two ceremonies 
have come to be mixed up: in the extreme case on one side there 
is no mutual ceremony—only an offering of weed by one bird to the 
other; at the other extreme we have the complete penguin dance 
as described on p. 499, where both cock and hen bring up weed ; 
and as intermediates we have mutual diving (p. 552) and mutual 
diving where the cock alone brings up weed (p. 552, end). 
Taken all in all, the courtship is chiefly mutual and self- 
exhausting: the excitatory, secondary-sexual forms of courtship 
such as weed-offering or pure display serve not as excitants to 
