520 LIFE : OUTLINES OF GENERAL BIOLOGY 



prospective factor is not disclosed in the physiological part of 

 the story. 



Mere sensory stimulation fails to account for the way a male 

 bird behaves to his territory. The physiological story needs to be 

 completed by a psychological story in terms of reference and revival 

 in the form of imagery. Thus mind integrates the reactions. 



Mr. Howard's book is one of the most important contributions 

 yet made to the study of bird behaviour. His patient and critical 

 observations show that the courtship has an intricacy, subtlety, and 

 individuality greater than we knew; the sequence of the chapters in 

 the sex-story has been made clearer; the importance of recognising 

 the creature as a whole has been corroborated; and the alleged 

 uselessness of the mind has been disproved. 



THE DETERMINATION OF SEX 



The determination of sex is one of the partially solved problems of 

 Biology. Over and over again the solution has slipped through the 

 fingers of science just when they seemed to be closing upon it. It is 

 peculiarly elusive, perhaps because it is near the central secret of 

 life itself. 



From ancient times a keen interest has been taken in the question 

 of the determination of the sex of the offspring. Many of the answers 

 are bound up with "theories of sex", which are legion. There can 

 be no doubt that the number of speculations connected with the 

 nature of sex has not fallen oft since Drelincourt, in the eighteenth 

 century, brought together two hundred and sixty-two "groundless 

 hypotheses", and since Blumenbach caustically remarked that 

 nothing was more certain than that Drelincourt 's own theory formed 

 the two hundred and sixty third. Subsequent investigators have at 

 least tried to add Blumenbach 's theory of a fundamental "Bil- 

 dungstricb" or formative impulse to the scrap-heap. 



The numerous answers offered to the question: What settles the 

 sex of the offspring? illustrate the progress of inquiry into the facts 

 of nature. As in so many other cases, the problem has been looked 

 at in three different ways. "F'or the theologian, it was enough to 

 say that 'God made male and female'. In the period of academic 

 metaphysics, still so far from ended, it was natural to refer to 

 'inherent properties of maleness and femaleness'; and it is still a 

 popular 'explanation' to invoke undefined 'natural tendencies' to 

 account for the production of males or females. Thirdly, it has been 

 recognised that the problem is one for scientific analysis." (Geddes 

 and Thomson, Evolution of Sex, 1889; revised edition 1901, p. 35.) 



There is a library of books and pamphlets dealing with the 

 determination of sex, but a large number — redolent as they are of 



