26 



was a conspicuous oviducal sinus, a vessel which had not been 

 described previously in snakes. 



The right carotid artery was not present in the adult, and to 

 compensate for this the left side of the head received its arterial 

 blood by means of three anastomoses — one beneath the medulla 

 oblongata, one beneath the fore-brain, and one beneath the 

 symphysis of the lower jaw. The part of the anterior cardinal 

 vein in the head of the embryo was completely replaced during 

 development by a new vessel, the lateral cephalic vein. 



Mr. Julian S. Huxley read a paper, communicated by Prof. G. 

 C. BouRKB, D.Sc, F.R.S., F.Z.S., containing an account of the 

 Courtship of the Redshank {Totanus calidris). 



The first purpose of this paper was to draw attention to the 

 many valuable results to be obtained by simple watching of very 

 common British birds ; and the second was to show how the facts 

 observed in the Redshank bore on the theory of Sexual Selection. 

 In this species there was no rival display between several males at 

 once : a single female was courted by a single male, as in Man. 

 The courtship started with a pursuit, the hen running in a 

 circuitous course, followed by the cock. The pursuit was followed 

 by a display, but only if the hen were willing that the courtship 

 should continue. During display the cock uttered a special note, 

 spread his tail, raised his wings above his back, and advanced with 

 a curious high -stepping action towards the now stationary female. 

 If the female so wished, pairing followed the display. But in quite 

 90 per cent, of observed courtships the female rejected the male, 

 either during the pursuit or during the display, by simply flying 

 away, when the cock was quite powerless to enforce his desires. 

 Thus the consent of the hen was absolutely necessary if pairing 

 were to take place, and this consent was usually withheld : in other 

 words, selection by the female was a reality in the Redshank. 



Other interesting points were as follows : — The plumage of the 

 two sexes was identical, and was decidedly cryptic when the birds 

 were at rest. During flight the white underside of the wings 

 and the white tail were conspicuously revealed, and probably 

 served as recognition marks. The significance of the red legs 

 was unknown. During display the male drew attention to 

 the underside of the wings by raising and vibrating them, to the 

 tail by fanning it out, and to the red legs by his slow, high 

 steps ; besides this he uttered a note heard at no other time. 

 Thus, since the actual colours and structures used in display were 

 found in both sexes, the only peculiarly male possession — the 

 only secondary sexual character of the Redshank — was a special 

 behaviour, devoted to showing ofi" these common colours and 

 structures in a special way. 



This seemed to show that secondary sexual differences in birds 

 were originally difierences of behaviour, and that only when 

 these were established did differences of coloiir and structure 

 come to be developed. 



