334 



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Inorganic Chemistry. A Textbook for Schools. By 

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A book for candidates for the School and Higher 

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An Introduction to Forecasting Weather. By P. Raymond 

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The Microscope. A Practical Handbook. By Lewis 

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General Astronomy. By H. Spencer Jones, M.A., B.Sc. 

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A Second Course in Engineering Science. By P. J. Haler, 

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Correspondence 



SECONDARY SEXUAL CHARACTERISTICS 



Sir, 



Jo the Editor of Discovery 



Dr. iNIottram's letter in your October number 

 raises a number of interesting points, to some of which 

 I will attempt to reply here. In the first place, I must 

 plead guilty (p. 201, 1. 17), imder the exigencies of space, 

 to attaching undue emphasis to the necessity for stimula- 

 tion of the female by the male. When " courtship " 

 occurs, this is its usual form ; but the reverse occurs, 

 e.g. in Phalaropes, and comparatively often there is 

 mutual stimulation. 



This brings me to Dr. Mottram's specific criticism. 

 He points out that many birds are alike in both sexes. 

 On the other hand, he fails to distinguish cases in which 

 the sexes are alike but protectively coloured, from those 

 where they are alike but brilliantly coloured and often 

 possessed of special adornments ; he further fails to 

 distinguish between those in which, although the sexes 

 are alike, the males alone perform " courtship " actions 

 (e.g., most Warblers), and those in which " courtship " 

 is a mutual affair — both sexes playing similar roles 

 (e.g. Herons, Grebes, Divers, Fulmars, etc.). 



As a matter of fact I have published (Proc. Zool. Soc, 

 1915) an account of the sexual ceremonies of the Crested 

 Grebe, where (and in the Auk 1916, and in Nature 1921) 

 the matter is discussed, and it is made, I think, clear 



that such " mutual courtship " may lead to the develop- 

 ment of bright colours and special structures in both 

 se.xes simultaneously. 



I have since then investigated the courtship of Divers, 

 Egrets, and other birds, and have a paper in press for the 

 Proc. Linnean Soc, to which I must refer Dr. Mottram 

 for a full theoretical discussion of the very interesting 

 questions he raises as to protective coloration and the 

 similarity of the two se.xes, together with numerous other 

 points. 



I am grateful to him for having pointed out the error 

 in my presentation. I should have said something 

 like this : "As mind develops, new complications arise. 

 Emotional stimulation is often necessary before sexual 

 union can be consummated. Largely from this cause 

 there have arisen the ceremonies and displavs of courting 

 animals." 



On the other hand, his criticism seems to me to be 

 based on a rather extensive lack of acquaintance with 

 the actual facts of " courtship " (to use that unsatis- 

 factory but generally-accepted term). No one who has 

 not studied in detail the actual occurrences associated 

 with display and other sexual ceremonies in birds can 

 have an idea of their complexity, or a right to indulge 

 in a priori theorising on the subject. I can at least 

 claim that the conclusions which I have reached — for 

 a detailed presentation of which, I repeat, I must refer 

 Dr. Mottram to my forthcoming paper — are based on 

 careful field study reinforced by over ten years' thinking 

 and digging into the literature. 



There are a great many complicating factors ; but there 

 is absolutely no doubt in my mind that there does exist 

 a relation between (i) a certain level of mental organisa- 

 tion ; (2) the performance of so-called courtship cere- 

 monies by one or both sexes ; (3) the acquisition of bright 

 colours, special structures, or stimulating qualities of 

 voice or odour, in one or both sexes. 



These characters developed in relation to courtship 

 can best be called by Poulton's term epigamic, as their 

 function is subsidiary to the union of male and female 

 sexual cells. 



It is an extraordinary thing how little work has been 

 done on a study of sexual ceremonies, even in common 

 British birds. For instance, until Eliot Howard's monu- 

 mental British Warblers appeared, in 1907 to 1914, no 

 satisfactory description, much less interpretation, had 

 ever been given of the relations of the sexes in any 

 single species of the group ! 



Anyone who is fond of natural history, has plenty of 

 patience, a field-glass and a notebook, and does not mind 

 now and again getting up early in the morning, can 

 contribute valuable material to this branch of science 

 and to the theory of sexual selection. The story even 

 of the Robin is not properly known ! The Tits, the Wood- 

 peckers, the Waders, the Wagtails, the Kingfisher — com- 

 paratively little has been discovered about the sexual 

 relationships of these groups, to name but a few as they 

 come into my mind. 



I cannot better close this letter than by appealing 

 to the amateur ornithologist, not merely to collect records 



