126 THE EVOLUTION OF SEX. 



SUMMARY. 



I. Suggested theories of the nature of male and female ; their number and 

 vagueness. Three recent developments — (a) Rolph's penetrating suggestion 

 of more nutritive females, less nutritive males ; (6) Minot's theory of the differ- 

 entiation of both kinds of sex-cells from a primitive hermaphroditism ; (c) the 

 conclusion of Brooks, that the males are more variable, and alone transmit 

 new variations. 



II. Nature of sex seen in its essence in the sex-cells. The fundamental 

 protoplasmic antithesis illustrated in the Protozoa, in the cells of higher animals, 

 in life-histories. The conception of a cell-cycle. The physiological import 

 of this,— the protoplasmic possibilities, preponderant anabolism, predominant 

 katabolism, and a relative equilibrium. The anabolic character of the ova. 

 The katabolic character of the sperm. 



III. The problem of the origin of sex, so little tackled, because of (a) the 

 blinding influence of teleological or utilitarian inquiries, (b) the number of 

 separate problems involved, {c) the isolation of sex and reproduction from the 

 general life of the organism and species. 



IV. A series from simple plants, showing the gradual appearance of 

 dimorphic sex-cells, with the physiological interpretation thereof. The dimor- 

 phism is the result of preponderant katabolism and anabolism, and this is the 

 origin of male and female. 



V. Illustrations of incipient dimorphism or sex among the Protozoa. 

 Special reference to the case of volvox. 



VI. Corroborative illustrations, — anther cells and Chara. 



VII. General conclusion, (a) from the sex-cells, (b) from incipient sex, (c) 

 from organs and tissues, (d) from the determination of sex, (e) from the charac- 

 ters of the sexes, — that male and female are the results and expressions of 

 predominant katabolism and anabolism respectively, with consequent confir- 

 mation of the speculation of Rolph and Minot. and in some measure also that 

 of Brooks. 



LITERATURE. 



Bro©ks, YV. K.— The Law of Heredity. Baltimore, 1883. 



Geddes, P. — Opp. cit., especially "Theory of Growth, Reproduction, Sex, 

 and Heredity," Proc. Roy. Soc. Edin., 1886; and Article "Sex, Encyc. 

 Brit., also " Restatement of Cell Theory, " Proc. Roy. Soc. Edin. 1S83-84. 



Minot, C. S. — Theorie der Genoblasten. Biolog. Centralblatt, II., p. 365. 



Rolph, YV. H. — Biologische Probleme. Leipzig, 1884. 



Sachs, J. — Text-book of Botany, edit, by Vines, second edition, 1882; and 

 Physiology of Plants, translated by Marshall Ward, 1887. 



Vines, S. H.— Physiology of Plants, 1886; article "Reproduction — Vege- 

 table," Encyc. Brit. 



Weissmann, A.— Opp. cit. 



