REPRODUCTION AND SEX 537 



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 contrast 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. 



Can We Control Sex? — Not many years ago it would have 

 seemed very "academic" to discuss the validity of the Manoilov 

 test for sex, or to speak about chromosomes in their relation to the 

 sex of calves and chickens on the farm. But we are more broad- 

 minded nowadays, especially since it has been proved up to the hilt 

 in instance after instance that very theoretical investigations are 

 often of the highest practical importance. As Bacon said, they are 

 fruit-bearing as well as light-giving. 



Now from several sides the citadel of sex is being stormed, and 

 the theoretical questions to which we have been referring are 

 essential parts of the attack. Suppose it be true that the sex of the 

 offspring depends primarily on the rate and rhythm of the meta- 

 bolism (or essential biochemical routine) in the egg-cells and sperm- 

 cells, then it may be possible to sway the metabolism to one side or 

 the other by altering the influences that play upon the germ-cells. 

 It may be possible to speed up or slow down the oxidations of the 

 egg or of the developing embryo. In some lower animals this has 

 already been done in various ways, and it may now be said that 

 sex is theoretically transformable or controllable. And apart from 

 the possibility of getting twelve cockerels to the dozen, and all that 

 sort of thing, a deeper physiological understanding of sex may lead 

 to methods of correcting sex-deficiencies or sex-exaggerations in 

 human beings. We quote a couple of sentences from one of Prof. 

 Riddle's recent papers: "Very diverse and special methods have 

 been used in controlling sex in several animals, but these are at 

 present largely or wholly inapplicable to the human and other 

 mammals. Yet if the ultimate effects of these several methods are 

 reducible to changes in what is known as metabolic rate, we can 

 later hope to employ in man and mammals other and new agencies 

 which can act directly and specifically on metabolic rate in the egg 

 and embryo." 



REVERSAL OF SEX. — There are some quite normal animals that 

 change their sex in the course of their lifetime. Thus the curious 

 primitive vertebrate called the hagfish {Myxine glutinosa), which 

 is far below the level of true fishes, which hves in deep water in the 

 North Sea and elsewhere, and sometimes bores into moribund or 

 dead fishes that have been caught on the fisherman's "deep lines", 

 is said to be first male and then female. This at least is the outcome 



