The determination of sex in animal development. 759 



spermatozoa. Such forms are spoken of as "protaiidrous hermaphro- 

 dites". As we have seen in earher pages, the spermatozoa of herma- 

 phrodites are products of transformed male-eggs. So that here again 

 we are confronted with an earher ripening of male-eggs or their pro- 

 ducts, and this is the same thing as the production of males before 

 the ripening of female-eggs. 



The ripening of more male- than female- eggs in the first in- 

 stance is of very great importance, for owing to the rôle played by 

 the female in sexual reproduction it converts the regulation 

 of the sexes into a self-adjusting one^). This was also 

 Hensen's and Düsing's-) conclusion, though the latter failed to re- 

 cognise the very simple way, in which it could be, and probably is, 

 brought to pass. He believed, that, for example, where the males 

 predominate, there is a greater probability of an early fertilisation of 

 the eggs, and that, therefore, there would result a much greater number 

 of female young. The consequence would, however, probably be the 

 opposite, a still greater preponderance of the males. 



In dealing with this problem attention may not be fixed upon 

 but one generation. With such any self- regulating arrangement has 

 not time to operate. Many generations may be required, before an 

 equilibrium can be established. A preponderance of males is only im- 

 portant for the generation, in which it happens, for the males have 

 no influence on the sexes of succeeding generations. What is the 

 deciding factor would appear to be a decrease of either the males or 

 the females of a race, such that the total number of individuals was 

 seriously affected. A decrease in the number or proportion of males 

 is hardly likely to cause a like diminution in the number of young 

 born : if it do so, it will probably bring the self-regulating mechanism 

 into action by the decrease in the number of females in the way to 

 be presently indicated. A diminution in the number of females will 

 in all probability bring about an increase in the number of j'oung 

 produced by each and all the females. As a result, owing to the 

 presence of more female-eggs than male ones in those later ripened, 

 there will, in the first instance, be something of an increase in the 

 number of female young. As the first progeny of these latter will 

 once again be predominantly male, in the third generation there will 



1) Probably in plants also. 



2) DcsiNG, C, Die ßegulirung des Geschlechtsverhältnisses bei der 

 Vermehrung der Menschen, Thiere und Pflanzen, in: Jena. Z. Naturw., 

 V. 17, 1883. 



