CHAPTER XVI 



SEX 



In the present chapter attention will be devoted to the cytological 

 aspects of the inheritance and determination of sex. 1 Much that is not 

 cytological in nature will enter into consideration, but it is far from 

 irrelevant: it has a direct bearing on the main cytological problem and 

 must be included in order that the latter may be placed in its proper 

 setting, and that the larger problem of sex may not be misrepresented by 

 being considered only from the cytological point of view. 



From early times few essentially biological matters have been of more 

 interest to man than that of the determination of sex. Until recent 

 years this interest has been prompted largely by practical motives: the 

 ability to control sex in man and his domesticated animals is something 

 which has long been desired. Of the many early ideas entertained on the 

 subject the majority were the outcome of defective generalization and 

 superstitious conjecture, and may be encountered in thinly veiled form at 

 the present day, but a review of them all would be out of place here. The 

 modern scientific interest in the problem of sex is far from being a purely 

 practical one. The great bulk of recent research has been done not 

 merely for the sake of the practical benefits which knowledge in this 

 field might confer, but mainly in the hope that it may lead to an under- 

 standing of the origin, nature, and biological significance of sex itself, 

 and to a solution of some of the problems of heredity. For this reason 

 studies have not been confined to man and his economically important 

 animals; any animal or plant, no matter how obscure, that will yield 

 evidence is exhaustively investigated, and there can be no doubt that 

 knowledge gained from such studies will, if sound, be directly applicable 

 to practical ends. 



Experimental Evidence for Sex-determination.— During the closing- 

 decades of the nineteenth century many researches were carried out in the 

 hope of identifying the controlling agency in sex-determination with one 

 or more of the environmental factors. The effects of light, temperature, 

 moisture, and nutrition were examined, and although a number of workers 

 believed their methods to be in a certain measure successful, the results 

 were on the whole inconclusive. Among all the ideas put forward the 

 most suggestive, in view of what has more recently been ascertained, 



1 See Correns (1907), Correns and Goldschmidt (1913), Morgan (1913), Doncaster 

 (1914), and the works cited at the beginning of the preceding chapter. 



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