Chap. XXVII. 



OF PANGENESIS. 363 



continued, to believe that the advantage thus gained is very 

 great. Besides these two important ends, there may, of course, 

 be others, as yet unknown to us, gained by the concourse of the 

 two sexes. 



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 is enabled to keep alive for even four 

 or five years within the spermatheca of a female insect, like- 

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

 questions which cannot be answered with any certainty. It 

 is, however, possible, that both sexual elements perish, unless 

 brought into union, simply from including too little formative 

 matter for independent existence and development; for cer- 

 tainly they do not in ordinary cases differ in their power of 

 giving character to the embryo. This view of the importance 

 of the quantity of formative matter seems probable from the 

 following considerations. There is no reason to suspect that 

 the spermatozoa or pollen-grains of the same individual animal 

 or plant differ from each other ; yet Quatrefages has shown in 

 the case of the Teredo, 8 as did formerly Prevost and Dumas 

 with other animals, that more than one spermatozoon is requisite 

 to fertilise an ovule. This has likewise been clearly proved by 

 Newport, 9 who adds the important fact, established by numerous 

 experiments, that, when a very small number of spermatozoa 

 are applied to the ova of Batrachians, they are only partially 

 impregnated and the embryo is never fully developed: the 

 first step, however, towards development, namely, the partial 

 segmentation of the yelk, does occur to a greater or less extent, 

 but is never completed up to granulation. The rate of the seg- 

 mentation is likewise determined by the number of the sperma- 

 tozoa. With respect to plants, nearly the same results were 

 obtained by Kolreuter and Gartner. This last careful observer 

 found, 10 after making successive trials on a Malva with more 

 and more pollen-grains, that even thirty grains did not fer- 

 tilise a single seed ; bat when forty grains were applied to the 



8 ' Annates des Sc. Nat.,' 3rd series, 1850, torn. xiii. 



9 « Transact. Phil. Soc.,' 1851, pp. 196, 208, 210 ; 1853, p. 245, 247. 



10 * Beitrage zur Kenntniss/ &c., 1844, s. 345. 



