398 PROVISIONAL HYPOTHESIS Chap. XXVH. 



and small as they must "be according to our hypothesis, has 

 no great weight. 



The units of the body are generally admitted by physiolo- 

 gists to be autonomous. I go one step further and assume 

 that they throw off reproductive gemmules. Thus an organ- 

 ism does not generate its kind as a whole, but each separate 

 unit generates its kind. It has often been said by naturalists 

 that each cell of a plant has the potential capacity of repro- 

 ducing the whole plant ; but it has this power only in virtue 

 of containing gemmules derived from every part. When a 

 cell or unit is from some cause modified, the gemmules derived 

 from it will be in like manner modified. If our hypothesis 

 be provisionally accepted, we must look at all the forms of 

 asexual reproduction, whether occurring at maturity or during 

 youth, as fundamentally the same, and dependent on the 

 mutual aggregation and multiplication of the gemmules. 

 The re-growth of an amputated limb and the healing of a 

 wound is the same process partially carried out, Buds 

 apparently inolude nascent cells, belonging to that stage of 

 development at which the budding occurs, and these cells are 

 ready to unite with the gemmules derived from the next 

 succeeding cells. The sexual elements, on the other hand, 

 do not include such nascent cells ; and the male and female 

 elements taken separately do not contain a sufficient number 

 of gemmules for independent development, except in the 

 cases of parthenogenesis. The development of each being, 

 including all the forms of metamorphosis and metagenesis, 

 depends on the presence of gemmules thrown off at each 

 period of life, and on their development, at a corresponding 

 period, in union with preceding cells. Such cells may be 

 said to be fertilised by the gemmules which come next in due 

 order of development. Thus the act of ordinary impreg- 

 nation and the development of each part in each being are 

 closely analogous processes. The child, strictly speaking, 

 does not grow into the man, but includes germs which slowly 

 and successively become developed and form the man. In 

 the child, as well as in the adult, each part generates the 

 same part. Inheritance must be looked at as merely a form 

 of growth, like the self-division of a lowly-organised uni- 



