Chap. XXVII. OF PANGENESIS. 397 



all the units of the body, besides having the universally ad- 

 mitted power of growing by self-division, throw off minute 

 gemmules which are dispersed through the system. Nor can 

 this assumption be considered as too bold, for we know from 

 the cases of graft -hybridisation that formative matter of some 

 Icind is present in the tissues of plants, which is capable of 

 combining with that included in another individual, and of 

 reproducing ever}^ unit of the whole organism. But we have 

 further to assume that the gemmules grow, multiply, and 

 ao-o-reo-ate themselves into buds and the sexual elements : 

 their development depending on their union with other 

 nascent cells or units. They are also believed to be capable 

 of transmission in a dormant state, like seeds in the ground, 

 to successive generations. 



In a highly-organised animal, the gemmules throAvn off 

 from each different unit throughout the body must be incon- 

 ceivably numerous and minute. Each unit of each part, as 

 it changes during development, and we know that some 

 insects undergo at least twenty metamorphoses, must throw 

 off its gemmules. But the same cells may long continue 

 to increase by self-division, and even become modified by 

 absorbing peculiar nutriment, without necessarily throwing 

 off modified gemmules. All organic beings, moreover, include 

 many dormant gemmules derived from their grandparents 

 and more remote progenitors, but not from all their pro- 

 genitors. These almost infinitely numerous and minute 

 gemmules are contained within each bud, ovule, sperma- 

 tozoon, and pollen-grain. Such an admission will be de- 

 clared impossible; but number and size are only relative 

 difBculties. Independent organisms exist which are barely 

 \isible under the highest powers of the microscope, and their 

 germs must be excessively minute. Particles of infectious 

 matter, so small as to be wafted by the wind or to adhere to 

 smooth paper, will multiply so rapidly as to infect within a 

 short time the whole body of a large animal. We should 

 also reflect on the admitted number and minuteness of 

 the molecules composing a particle of ordinary matter. 

 The difficulty, therefore, which at first appears insurmount- 

 able, of believing in the existence of gemmules so numerous 

 S9 



