408 THE ZOOLOGIST, 



immediately, and with a special impetus, followed by a resort to 

 the nest, for that purpose.* 



(11) The lengthy sojourn of the female on the nest, during 

 which, visits are made by the male for the purpose of coition 

 upon it, this taking place either (a) before any of the eggs have 

 been laid, as observed, or (b) after one or more of them have 

 been laid, as inferred from the conduct of the birds, in prepara- 

 tion for this act ; these facts suggesting possible stages through 

 which the earlier use of the nest, as a pairing-place, has passed 

 into the later one, and incubation, owing to the presence of 

 both parents, in contiguity with the eggs, become common to 

 both, a fact which, seeing that they are only laid by one of them, 

 one would not, prima facie expect to find in any case.t 



(12) The habitual daily presence, during considerable periods 

 of time, of both the male and female bird, on a certain spot 

 where pairing takes place, and where the nest is subsequently 

 gradually built, with continuance of such pairing upon it, thus 

 greatly strengthening the above surmise. J 



(13) Eeversed functioning as between the sex.es> in coitu, 

 suggesting the essential oneness, in both, of the sexual feelings 

 from, or in connection with which, all sexual movements, antics, 

 etc., must have originated ; which makes it easier to suppose 

 that any transforming process of evolution in such movements, 

 in any direction, has been essentially the same in both, as also 

 that any of them may have passed from one sex to the other, 

 with consequent increase, decrease, or cessation of the activities 

 thus transferred, in either, according to the ordinary law of the 

 utilisation of beneficial variations, through natural selection. § 



(14) The recurrence of sexual actions and movements, 

 including those of true courting display, such as ordinarily 

 precede coition, immediately after this has taken place, on the 



-'Zoologist,' September, 1901, pp. 343-4; June, 1914, pp. 213-14. 

 ' Wild Life,' June, 1915, p. 178 ; July, 1915, pp. 32-4 ; August, 1915, pp. 38-9, 

 41-2. 



f ' Zoologist,' May, 1901, pp. 162-5 ; ' Wild Life,' April, 1914, p. 212. 



\ ' Wild Life,' May, 1915, p. 153 ; June, 1915, pp. 177-8. The facts are 

 brought out more fully in my actual notes (unpublished), of which the paper 

 is a resumS. 



§ ' Zoologist,' September, 1901, pp. 341-2 ; May, 1902, pp. 196-7 ; May, 

 1907, pp. 168-9. ' Wild Life,' July, 1915, pp. 31-5 ; August, 1915, pp. 38-42. 



