REPRODUCTION AND SEX 499 



egg-sacs of many female water-fleas, e.g. Cyclops, are extra things 

 on the female's part. 



MODE OF ORIGIN OF SEX-CHARACTERS.— If we turn aside 

 from the hypothesis that sex-characters arose by the hereditary 

 accumulation of the direct results of somatic modifications, whether 

 functional or environmental, we are led to the view that they arose 

 as germinal variations or mutations. That the germinal origin of 

 variations or of mutations is wrapped in obscurity, makes all phylo- 

 genetic aetiology difficult; there is no special difficulty in regard to 

 sex-characters ; the problem of their origin is probably in essence 

 like that of any other characters. 



Without straying far from our present path, we may here state 

 some of the possibilities as regards the origin of variations, (a) Fluc- 

 tuations in the nutritive stream may bring about changes in the 

 germ-cells. (6) The opportunities afforded in maturation and fertilisa- 

 tion may bring about a shuffling of the chromosome cards, (c) Ex- 

 ternal changes may serve as trigger-pulling variational stimuli to 

 the highly complex germ plasm, (d) There is a tendency in matter to 

 complexify, no more explicable than gravitation, but real; perhaps the 

 living unit utilises this in its {e) unconscious germinal experiments in 

 self-expression, for that is what we believe mutations, at least, to be. 



Let us suppose, then, that a germ-cell already predisposed to 

 develop into an ovum-producer was the seat of a variation, say in 

 the determinants or factors corresponding to the future ovary. Let 

 us suppose that this variation was in the direction of producing an 

 accessory yolk-gland. In the course of development the determinant 

 or factor, if consistent with the rest of the constitution, is actualised 

 and there is the beginning of a yolk-gland — an advantageous addi- 

 tion obviously. In the course of time the organism reproduces and 

 its germ-cells have entailed on them (in accordance with the con- 

 ception of germinal continuity) the determinant or factor of a yolk- 

 gland. But the difficulty immediately arises in the mind that this 

 new hereditary item will be found not only in the germ-cells which 

 will develop into females (where it will be relevant), but also in 

 the germ-cells which will develop into males (where it will be irrele- 

 vant). The most obvious difficulty, then, is what will happen to 

 the yolk-gland determinant in those germ-cells that are going to 

 develop into males. The answer is that it will remain latent, not 

 because its expression would be irrelevant, which is a finalistic idea, 

 but because it arose as a variation in a gamete predisposed to 

 develop into a female. It is solidary with femaleness; which, for us, 

 means a metabolism-ratio or rhythm with relatively preponderant 

 anabolism. Metaphorically, it is a seed which will germinate in 

 female soil, which will not germinate in male soil, though it will 

 remain latent there. 



