176 THE POPULAR SCIENCE MONTHLY. 



ration here is only partial. Preceding the condition represented by 

 the hydra, and connecting with the last {d), we ought to find one in 

 which two similar cells elaborated by the same organ unite or conju- 

 gate to commence the new life — a condition in which the sexual ele- 

 ments are potentially but not visibly differentiated. This condition is 

 realized, as far as we yet know, only in the conjugation of unicelled 

 organisms. 



(/.) BisexuaUty. — The next step is of course the complete differen- 

 tiation not only of the sexual elements, but also of the sexual organs. 

 This is bisexuality or hermaphroditism, very common, as is well known, 

 among lower animals and almost universal among plants. 



{g.) Uniseximlity. — The last step is the separation of the sexes in 

 different individuals. This of course effectually prevents self-fertiliza- 

 tion in both animals and plants. But cross-fertilization must be in- 

 sured. This, as already seen, is done by winds and insects in the case 

 of plants, and by waves and currents in some lower animals. These 

 agents do not, however, insure fertilization in higher animals. There- 

 fore, in them there is added sex-appetite and all associated feelings for 

 tbat purpose. 



(A.) After the separation of the sexes has been a sufficiently long 

 time accomplished, the evidence in the ontogeny of former conditions 

 is gradually obliterated — the memory of them is lost. 



6. Differentiation of the Two Sexual Individuals. — We have 

 now reached complete unisexuality — i, e., the separation of the sexes 

 into different individuals, but not yet the very best results. Unisexuality 

 is better than the orchid and snail method of mutual fertilization, only 

 because the latter method is incapable of further differentiation, and 

 therefore of any further improvement of results. In cases of mutual 

 fertilization the individuals are all alike, except these small individual 

 differences, which occur even in self -fertilizing bisexuals. But as soon 

 as the sexes are separated into different individuals, then there is room 

 for indefinite differentiation of the two sexual individuals. Now, as 

 we go up the animal scale we find that such differentiation has indeed 

 taken place, and that progressively. The sexual differences — i. e., the 

 difference between male and female individuals of the same species 

 — become greater and greater as we rise in the scale. They are also 

 greater, we believe, in the higher as compared with the lower races of 

 man, and in the cultivated classes as compared with the uncultivated 

 classes. From this sexual difference springs sexual attractiveness, and 

 from this lowest root, it is not too much to say, springs much if not all 

 our noblest altruistic nature. For, as our physiological functions are 

 primarily divisible into two great groups, viz., the nutritive and the 

 reproductive, the one including all that assemblage of functions which 

 conserve the individual life, the other all that assemblage of functions 

 which conserve the continuous life of the species, so all our psychical 

 functions are also primarily divisible into two groups, the egoistic and 



