r66 THE GERM-PLASM 



3. Comparison of the Process of Gemmation in 

 Animals and Plants 



Various stages may be recognised in the different kinds of 

 gemmation with regard to the kind of idioplasm concerned in 

 the process. The simplest form of budding is seen in those 

 plants in which the production of a new ' person ' by budding 

 always originates from a single cell. We must therefore 

 assume that the idioplasm of this cell contains all the deter- 

 minants of the shoot, and very probably those of the root 

 also. For most of the shoots of a plant, when they have been 

 cut off from the stem, are capable of giving rise to roots under 

 favourable circumstances. This does not as a rule occur under 

 normal conditions, — that is to say, while the shoot is still con- 

 nected with the parent-plant. The ' blastogenic idioplasm' 

 cannot be quite identical with germ-plasm proper ; for although 

 precisely the same parts may arise from it as from the fertilised 

 egg-cell, the different succession of cells which results in embrv- 

 ogeny and in gemmation indicates that the determinants must at 

 any rate be differently arranged in the idioplasm, and that possibly 

 their proportional number is also different. '• Blastogenic idio- 

 plasm ' and geriii-plasni Diay in a sense be 7'egarded as ' isomeric ' 

 idioplasms, using the term in an analogous sense to that of 

 isomeric chemical compounds. 



The same would be true as regards such animals as Hydroids, 

 in which the formation of a bud originates from a single cell. 

 In this case, again, the resemblance between embryonic develop- 

 ment and the process of gemmation, although to a certain extent 

 approximate, is not a complete one ; and it must again be 

 assumed that the wJiole of the determinants of the species are 

 contained in the blastogenic idioplasm, — not only those which 

 as a rule undergo development, but also those required for the 

 formation of the attached ends in the case of Hydroids, or of 

 roots in the case of plants. This conclusion is supported by the 

 phenomena of budding in polypes like Hydra, in which the buds 

 regularly become detached, and carry on an independent exist- 

 ence. In such cases the daughter-polypes do not develop a 

 'foot' until they become detached from the parent. 



The next stage in the process of budding is seen in the 

 Polyzoa. All the determinants of the species from which tlie 

 bud is formed are no longer contained in a single cell, but are 



