442 LAWS OP MULTIPLICATION. 



multiply by a process allied to gemmation, yet this is not 

 characteristic of the class. A leading trait of these highest 

 groups, to which the largest members of the vegetal king- 

 dom belong, is that agamogenesis has so far ceased that it 

 does not usually originate independent plants. Though the 

 axes which, budding one out of another, compose a tree, 

 are the equivalents of asexually-produced individuals; yet 

 the asexual production of them stops short of separation. 

 These vast integrations arise where spontaneous disintegra- 

 tion, and the multiplication effected by it, have come to an 

 end. 



Thus, not forgetting that certain Phasnogams, as Begonia 

 pliyllomaniaca, revert to quite primitive modes of increase, 

 we may hold it as beyond question that while among the 

 most minute plants asexual multiplication is universal, and 

 produces enormous numbers in short periods, it becomes step 

 by step more restricted in range and frequency as we ad- 

 vance to large and compound plants; and disappears so 

 generally from the highest and largest, that its occurrence is 

 regarded as anomalous. 



336. Parallel examples furnished by animals make clear 

 the purely quantitative nature of this relation under its origi- 

 nal form. Among the Protozoa, as among the Protophyta, 

 there occurs that process by which the individuality of the 

 parent is wholly lost in producing offspring the breaking 

 up of the parental mass into a number of germs. Some of 

 the Infusoria, as for instance those of the genus Kolpoda 

 and several allied genera, become encysted and subsequently 

 break up into young ones. The more familiar mode 



of increase among these animal-aggregates of the first order, 

 by fission, though it sacrifices the parent individuality by 

 merging it in the individualities of the two produced, sacri- 

 fices it less completely than does the dissolution into a great 

 number of germs. Occurring, however, as this fission does, 

 very frequently, and being completed, in some cases that 



