464 THE ZOOLOGIST. 



my observations to this effect were recorded, headed " Intersexual 

 Selection " (which perhaps is not a good term). I discuss the evidence 

 for this. I did indeed, in the case of the Fulmar Petrel, see some- 

 thing a good deal resembling these shaking bouts of the Grebes, but 

 the development of the habit along aesthetic lines was more than 

 suggested by the way in which the pair opened their bills at each 

 other, thereby displaying a handsomely coloured buccal cavity — 

 which it was equally open to them to conceal. Yet the shaking (or 

 swaying) seemed to be enjoyed for its own sake. Since the Grebes 

 have their crests, as well as the habit of "nebbing," this part of the 

 ceremony may, in either case, represent a bye-prcduct. 



(2) " The hen took hold of the dangling end of the weed, which 

 the cock was carrying, and then they ' chassed, with little waddling 

 steps ' from side to side. I think Selous is mistaken ; such an action 

 as he describes would be impossible on open water " (p. 532). This is 

 not quite exactly what I say, though my use of the word chassc lends 

 itself, almost unavoidably, to such a recollection of my meaning. 

 But the " little waddling steps " were " now forwards, now back- 

 wards, but not going more than a few inches either way," and then 

 I continue, " I would say that they chassed — for it had that effect — 

 but the motion was as described, and not from side to side " (Zool., 

 1901, p. 314). My subsequent observations on the Bed-throated 

 Diver (a heavier bird) prove that there is no impossibility in such an 

 action as this on water absolutely open. Consequently there is no 

 reason why I should have been mistaken, and the vivid mental 

 picture which I retain of the birds thus moving will not allow me to 

 think that I was. 



(3) " More light is needed on the habit " (of sexual sporting with 

 weed). "It is perhaps connected with the arranging of the weeds 

 on the nest by both birds together " (p. 533). My observations go to 

 show that there is an association of ideas in the minds of various 

 species of birds between the mandibulation of materials composing, 

 or proper to compose, the nest, and coition on the nest. The long 

 holding up of an article of mine keeps back some of my most striking 

 evidence in this direction, but I may refer to the last instalment of 

 my Icelandic diary (Zool., 1914, p. 213), to " Wild Life," April, 1914 

 (p. 212), and also, for examples of such association, in the case of 

 the Great Crested Grebe itself, when the bird is on the nest, and 

 mandibulates the materials of which it is composed, to Zool., 1901 

 (pp. 342-344). 



(4) " The cock of course uses his special platform to rest on, so it 



