OBJECT OF SEXUALITY. 799 



the view of the most prominent mycologists, very probable that they possess no sexual 

 organs whatever. 



The consideration of this fact, which we could easily make good by numerous 

 other examples, leads directly to the question, what is the precise object which Nature 

 attains by the production of sexual organs and by sexual propagation ? 



This question appears the more pertinent when we see, on the other hand, with 

 what care (if this picturesque expression is allowable) Nature proceeds in very many 

 cases to ensure the union of the sexual cells, and the production of sexually produced 

 descendants: all the marvellous adaptations of Dichogamy, Heterostylism, Herko- 

 gamy, and other arrangements, which we have studied with the aid of examples in 

 the preceding lecture, may be looked upon in this sense. 



Meanwhile, as De Bary has already stated elsewhere, we shall probably have 

 to concede that, as matter of fact, we simply know that fertilisation is in many 

 cases demonstrated by experience to be an indispensable process to the plants 

 concerned, in many other cases this is simply not so, and we have in the meantime no 

 ground for assuming that all organisms must behave similarly in this respect. This 

 somewhat unsatisfactory conclusion, however, does not prevent the assumption that 

 in the many cases where reproduction is regularly attained by fertilisation, special 

 advantages are connected with it, which in the contrary case are simply attained 

 in some other manner, or perhaps in certain cases are even not attained. . A few of 

 such probable advantages may here be brought forward. 



Darwin, on the basis of the comprehensive results of the artificial breeding of 

 animals and plants, has demonstrated to realisation the idea already expressed by 

 Sprengel, that in all sexual reproduction the chief point is to ensure the crossing of 

 individuals of the same species, of which detailed illustrations have been given in 

 the preceding lecture. It also results from the experimental investigations of Darwin, 

 Hildebrand, and others, that just as so-called incest among some domestic animals 

 results in the production of few or feeble descendants, so also does the continued self- 

 fertilisation of androgynous flowers, whereas in like species of plants the crossing of 

 different individuals results in the production of vigorous seeds. Supported by Darwin's 

 authority, one is now very ready to suppose that incidental abnormalities or diseased 

 conditions are equilibrated by means of the sexual intermixture, and are rendered 

 uninjurious in the descendants. In addition to some other considerations, mention 

 should here be made, however, o^ the very large number of plants which certainly 

 maintain themselves asexually through hundreds and thousands of generations 

 without the slightest ground existing for supposing that they are gradually degene- 

 rated by the process. 



On the other hand, we may here think of the fact, established by artificial 

 hybridisation, that, by means of the sexual intermingling of individuals from diflferent 

 sources, the variability of the descendants is increased, and that in this way the number 

 of the different organic forms may have gradually been multiplied : though even here 

 also it is not to be forgotten that the formation of varieties sometimes occurs also 

 during asexual reproduction ; at any rate the majority of the varieties of Potato have 

 probably been produced asexually. 



And nevertheless in all the suppositions there again exists the perception that, with 

 increasing complexity of organisation both in the animal and vegetable kingdoms, the 



