1500 THE STORY OF THE UNIVERSE 



As in the case of flowers, I have as yet failed, after 

 consultation with one of the highest authorities, 

 namely, Professor Huxley, to discover a single her- 

 maphrodite animal with the organs of reproduction 

 so perfectly inclosed that access from without, and 

 the occasional influence of a distinct individual, can 

 be shown to be physically impossible. Cirripeds long 

 appeared to me to present, under this point of view, 

 a case of great difficulty; but I have been enabled, 

 by a fortunate chance, to prove that two individuals, 

 though both are self-fertilizing hermaphrodites, do 

 sometimes cross. 



It must have struck most naturalists as a strange 

 anomaly that, both with animals and plants, some spe- 

 cies of the same family and even of the same genus, 

 though agreeing closely with each other in their 

 whole organization, are hermaphrodites, and some 

 unisexual. But if, in fact, all hermaphrodites do oc- 

 casionally intercross, the difference between them 

 and unisexual species is, as far as function is con- 

 cerned, very small. 



From these several considerations and from the 

 many special facts which I have collected, but which 

 I am unable here to give, it appears that with animals 

 and plants an occasional intercross between distinct 

 individuals is a very general, if not universal, law of 

 nature. 



To sum up, as far as the extreme intricacy of the 

 subject permits, the circumstances favorable and un- 

 favorable for the production of new species through 

 natural selection. I conclude that for terrestrial pro- 

 ductions a large continental area, which has under- 



