September 29, 192 1] 



NATURE 



153 



X the material brought back by the expedition 

 will also help to clear up the vexed question as to 

 the races of the Puffin [Fratercula arctica)^ as to 

 which there is much division of opinion. 



Some interesting- observations bearing on the 

 sexual selection theory were made by Julian S. 

 Huxley on the Red-throated Diver {Colymbus stel- 

 latus), confirming and extending the conclusions 

 reached by him in his paper on the courtship of 

 Podiceps cristatus (Proc. Zool. Soc., 1914)- After 

 the birds have mated for the season, elaborate 

 courtship ceremonies take place between the mated 

 pair. At times the two birds swim near each other 

 with necks arched and the open beak half sub- 

 merged, uttering a special cry. At others, one 

 bird will dive all round and about the other, 

 sometimes emerging almost vertically from the 

 water, as does Podiceps. The active performer 

 in such cases may be either the male or the 

 female. 



There thus exist, as in the Crested Grebe, muiital 

 nuptial ceremonies. The bird's bright colouring 

 and special nuptial activities are connected with 

 the bird's sexual life, but not secondary sexual 

 characters — epigamic, but not sex-limited. 



Of particular interest were the observations 

 made on the period during which the birds are 

 separating into pairs for the season. At this time, 

 too, they indulge in special ceremonies, in which. 

 however, rarely two, but usually three (or even 

 four), individuals participate. The birds submerge 

 the whole body with the exception of the breast ; 

 the neck is thrust slightly forward and the head 

 held out, so that the appearance is that of a minia- 

 ture Plesiosaur. In this attitude the birds plough 

 through the water, as if running races. This 

 ceremony was never observed later, and is cer- 

 Itainly connected with the choice of mates. Most 

 iremarkable of all, it appears almost certain that 

 itwo females may thus " compete " for a single 

 {male as well as vice versa. In any event, we have 

 jas a new feature that in this species the mutual or 

 jcommon nuptial activities of the two sexes extend 

 e\-en into the pairing-up period, where, if any- 

 where, sex-limited display and Darwinian sexual 

 selection might be expected. This period was not 

 observed in the previous work on Podiceps. The 

 need for some theory of " mutual selection " to 

 supplement the Darwinian theory of sexual selec- 

 ition is thus further emphasised. 



Favourable opportunities for observing the nup- 

 tial activities of Phalaropes and Purple Sandpipers, 

 in both of which reversed sexual coloration and 

 habits occur, were unfortunately very few. It is, 

 however, suggested that (i) the pressure of Arctic 

 life acts as an encouragement to small size in the 

 w^aders ; {2) that, per contra, the short breeding 

 season requires the eggs to be large, in order that 

 their development may be hastened ; this, in its 

 turn, will limit the reduction in size of the female; 

 {3) the female will therefore tend to be bigger than 

 the male; (4) in almost all birds (excluding Rap- 

 tores) brighter colour of the male accompanies 

 larger size. Presumably size, pigmentation, and 

 psychological activity are all controlled together by 

 the endocrine secretion of the gonad. It is thus 

 probable that larger size of the female in these 

 species will be associated with that type of meta- 

 bolism which favours more intense pigmentation ; 

 (5) the more protectively coloured male could then 

 more advantageously undertake incubation. 



A discussion of this suggestion, however, would 

 involve the handling of large bodies of evidence. 

 It is, in any event, clear that the condition has 

 developed from one in which both sexes were simi- 

 larly coloured, and both shared the duties of 

 incubation. 



To sum up, we have here a series of nearly three 

 hundred skins as well as about five hundred eggs, 

 together with full diaries and field notes from mem- 

 bers of the expedition. It is hoped that the reports 

 on these collections will embody what is already 

 known of the Spitsbergen and Bear Island group, 

 and provide us with a dependable and handy 

 manual on the birds of the archipelago. The com 

 ing of the oil engine has already affected the 

 fauna considerably, and probably will do so even 

 more in the future, and it is important to record 

 the changes of the last ten or fifteen years. 

 Koenig's fine work is bulky and expensive, and a 

 concise account of the bird life, embodying the 

 results of the present expedition, would be a most 

 valuable work of reference as well as a permanent 

 memorial of what is perhaps the only serious orni- 

 thological work undertaken by English men or 

 women in the Arctic since Mr. Henry Pearson's 

 last voyage to Russian Lapland more than twenty 

 years ago, with the sole exception of Miss Havi- 

 land's adventurous journey to the mouth of the 

 Yenisei in 1914. 



The Present Position of the Theory of Descent, in Relation to the Early History 



of Plants.^ 



Bv Dr. D. H. Scott, F.R.S. 



T T has long been evident that all those ideas of 

 evolution in which the older generation of 

 naturalists grew up have been disturbed, or, 

 indeed, transformed, since the re-discoverv of 

 Mendel's work and the consequent development 



\bridged from the presidantial address delivered to Section K (Ootany) 

 - British Association at Edinburgh on September 9. 



NO. 2709. VOL. 108] 



of the new science of genetics. Not only is the 

 " omnipotence of natural selection " gravely 

 impugned, but also variation itself, the founda- 

 tion on which the Darwinian theory seemed to 

 rest so securely, is now in question. 



The small variations, on which the natural 

 selectionist relied so much, have proved, for the 



