262 THE EVOLUTION OF SEX. 



SUMMARY. 



1. In most of the emotions, and in the simpler intellectual processes, 

 there is common ground between animals and men. This is especially true 

 of the emotions associated with sex and reproduction. 



2. The love of mates has its roots in physical sexual attraction, but has 

 been gradually enhanced by psychical sympathies. 



3. The means of sexual attraction rise from the crude and physical to 

 the subtle and psychical, wiih the growth of love. 



4. The intellectual and emotional differences between the sexes are 

 correlated with the deep-seated constitutional differences. Males and 

 females are complementary, each higher in its own way. 



5. The love for offspring has grown as gradually as the love for mates. 

 Even lactation and maternal care may be in part egoistic. Except in a 

 few precociously tender animals, genuine love for offspring is only emphatic 

 in birds and mammals, where the reproductive sacrifice of the mother has 

 also been increased. 



6. The cuckoo illustrates the evolution of a criminal habit, mainly due 

 to constitutional conditions. 



7. Egoism and altruism have their roots in the primary hunger and 

 love, or nutritive and reproductive activities. The divergent streams of 

 emotion and activity have a common origin, subtly mingle at various turn- 

 ing-points, and ought to blend more and more in one. 



LITERATURE. 



See works on Sexual Selection cited at Chap. I. 



EiMER, G. H. T. — Die Entstehung der Arten auf Grund von Vererben 



Erworbener Eigenschaften nach den Gesetzen Organischen Wachsens. 



Jena, 1888. 

 BiJCHNER, L. — Liebe und Liebeslel)en in der Thierwelt. Berlin, 1879. 

 Roi.FH, W. Yi. — Op. cit. 

 Romanes, G. J. — Animal Intelligence. Internat. Sci. Series. Fourth 



edition, 1886; and Mental Evolution in Animals, by the same. 

 Thomson, J. A.— A Theory of the Parasitic Habit of the Cuckoo. Proc. 



Roy. Phys. Soc. Edin. 1888. 

 Sec also Carus Sterne's most admirable of general natural history 



books — Werden und Vergehen. Third edition. Berlin, 1886. 

 Ploss. — Das Weib in der Natur und Volkerkunde. Second edition. 



Leipzig, 1887. 

 Mantegazza, p. — Die Physiologic der Liebe; Die Hygiene der Liebe ; 



Anthropologisch-Kulturhistorische Studien iiber die Geschlechtsver- 



haltnisse des Menschen. Jena. 



