134 THE EVOLUTION OF SEX. 



SUiMiMARV 



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

 and vagueness. Three recent developments — (a) Rolph's penetrating sug- 

 gestion of more nutritive females, less nutritive males ; (/') Minot's tlieory 

 of the differentiation of both kinds of sex-cells from a primitive her- 

 maphroditism ; {c) the conclusion of Brooks, that the males are more vari- 

 able, and alone transmit new variations. 



2. 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 physiolo- 

 gical import of this, — the protoplasmic possibilities, preponderant ana- 

 bolism, predominant katabolism, and a relative equilibrium. The anabolic 

 character of the ova. The katabolic character of the sperms. 



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

 blinding influence of teleological or utilitarian inquiries, (/-') the number of 

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

 the general life of the organism and species. 



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

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

 dimorphism is the result of preponderant katabolism and anabolism, and 

 this is the origin of male and female. 



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

 Special reference to the case of volvox. 



6. Corroborative illustrations, — anther cells and Chara. 



7. General conclusion, — (a) from the sex-cells, {i) from incipient sex, (c) 

 from organs and tissues, (c/) from the determination of sex, {e) from 

 the characters of the sexes, — that- male and female are the results and 

 expressions of i:)redominant katabolism and anabolism respectively, with 

 consequent confirmation of the speculations of Rolph and Minot, and in 

 some measure also of that of Brooks. 



LITERATURE. 



Brooks, \V. K.— The Law of Heredity. Baltimore, 1SS3. 



Geddes, p. — 0/>/>. c/L, especially " Theory of Growth, Reproduction, Sex, 

 and Heredity," Proc. Roy. Soc. Edin., 18S6 ; and Article "Sex," 

 Encyc. Brit., also "Restatement of Cell Theory," Proc. Roy. Soc. 

 Edin., 1883-84. 



Minot, C. S.--Theorie der Genoblasten. Biolog. Centralblatt, II., 



P- 365. 



Rolph, W. H. — Biologische Probleme. Leipzig. 1S84. 



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- 

 Vegetable," Encyc. Brit. 



Welsmann, a. — 0/>/>. lit. 



