Chap. XXVIL OF PANGENESIS. 355 



ordinary generation for the concourse of the two sexual 

 elements. 



Seeds and ova are often highly serviceable as the means of 

 disseminating plants and animals, and of preserving them 

 during; one or more seasons in a dormant state : but un- 

 impregnated seeds or ova, and detached buds, would be equally 

 serviceable for both purposes. We can, however, indicate 

 two important advantages gained by the concourse of the 

 two sexes, or rather of two individuals belonging to opposite 

 sexes; for, as I have shown in a former chapter, the structure 

 of every organism appears to be especially adapted for the 

 concurrence, at least occasionally, of two individuals. When 

 species are rendered highly variable by changed conditions 

 of life, the free intercrossing of the varying individuals 

 tends to keep each form fitted for its proper place in nature ; 

 and crossing can be effected only by sexual generation ; but 

 whether the end thus gained is of sufBcient importance to 

 account for the first origin of sexual intercourse is extremely 

 doubtful. Secondly, I have shown from a iarge body of 

 facts, that, as a slight change in the conditions of life is 

 beneficial to each creature, so, in an analogous manner, is the 

 change effected in the germ by sexual union with a distinct 

 individual ; and I have been led, from observing the many 

 widely-extended provisions throughout nature for this purpose, 

 and from the greater vigour of crossed organisms of all 

 kinds, as proved by direct experiments, as well as from the 

 evil effects of close interbreeding when long continued, to 

 believe that the advantage thus gained is very great. 



Why the germ, which before impregnation undergoes a 

 certain amount of development, ceases to progress and 

 perishes, unless it be acted on by the male element; and 

 why conversely the male element, which in the case of some 

 insects is enabled to keep alive for four or five years, 

 and in the case of some plants for several years, likewise 

 perishes, unless it acts on or unites with the germ, are 

 questions which cannot be answered with certainty. It is, 

 however, probable that both sexual elements perish, unless 

 brought into union, simply from including too little formative 

 matter for independent development. Quatrefages has shown 



