CONCLUSION 509 



that they differ in respect to their metabolic processes," or, again, 

 " Upon what conditions within the fertilised egg does the sexual 

 differentiation depend ? In some way, we may now be reason- 

 ably sure, upon the physiological reactions of nucleus and 

 protoplasm." 



ii. Conclusion 



In conclusion, our view is that the difference between an 

 ovum-producer and a sperm-producer is fundamentally a differ- 

 ence in the balance of chemical changes, i.e. in the ratio of ana- 

 bolic and katabolic processes, which may, of course, have its 

 structural expression in the relation of nucleoplasm and cyto- 

 plasm. Nor do we leave this difference in metabolism-rhythm 

 as a mere vague phrase, for we see its 1 analogue in the contrast 

 between the ovum and the spermatozoon (though it is quite 

 unwarrantable to think of these as being in themselves respec- 

 tively female and male cells), between the macrogamete and the 

 microgamete, between the encysted and the flagellate cell, 

 between the plant and the animal, and in many a familiar con- 

 trast all through the series of Organisata. We adhere, in short, 

 to the thesis of The Evolution of Sex, that the sex-difference 

 is but one expression of a fundamental alternative in variation, 

 to be seen throughout the world of life. 



