MULTIPLICATION BY GEMMATION I7I 



must then have been passed into certain series of cells in the 

 course of ontogeny. 



Whether the process of budding has actually been derived 

 from that of the doubling of the egg or not, it seems to me to be 

 certain at anv rate that the first process undergone by the idio- 

 plasm initst have been that of the doubling of the ids of the 

 ^ervt-plasm in the fertilised egg-cell^ and that this was not con- 

 nected with the division of the egg-cell ; one half of the germ- 

 plasm consequently remained in an unalterable and inactive 

 condition, in which, however, it was capable of development. 

 This blastogenic germ-plasm was then supplied to one of the 

 first segmentation-cells in the form of accessory idioplasm ; and 

 from these it was passed on through certain series of cells in an 

 unalterable condition, only becoming active when it had reached 

 certain parts in the fully formed animal, in which it then caused 

 gemmation to occur. 



It does not seem to be inconceivable that the process of bud- 

 ding owes its origin phyletically to such a spontaneous division 

 and doubling of the germ-plasm, and that this was originally 

 connected with the inactivity of half the germ-plasm : its con- 

 nection with the doubling of the ovum was consequently not 

 such as was indicated above, — that is to say, gemmation did not 

 owe its origin to the doubling of the egg, but both processes orig- 

 inated primarily in the division and doubling of the gerni-plasni 

 of the egg-cell^ to which in any case the doubling of the ^g% must 

 be due. The difference between the two processes would then 

 consist in the fact that in budding one-half of the germ-plasm 

 would pass into the inactive condition, while in the doubling of 

 the e£2 both halves would at once become active. 



The modifications of the idioplasm which result in gemmation 

 must become more complex as soon as two, or all three, of the 

 germinal layers take part in the process, instead of one only. 

 In such cases the blastogenic germ-plasm must undergo disin- 

 tegration at certain ontogenetic stages, eg., at the separation of 

 the ectoderm from the endoderm, and again at the separation of 

 the mesoderm from one of the two primary germinal layers. 

 Precisely the same combination of determinants need not 

 necessarily be produced by the disintegration of the accessory 

 germ-plasm into two or three groups of unalterable accessory 

 idioplasm, such as are formed in embryogeny. We can thus 

 explain the origin of endodermal organs from the ectoderm cells 



