i42 LAWS OF MULTIPLICATION. 



The Protophytes that perpetually subdivide, the merely- 

 cellular Algce that shed their tetraspores, the Acrogens that 

 spontaneously separate their fronds and drop their gemmEe, 

 show us an extra mode of multiplication which, among flower- 

 ing plants, is exceptional. This extra mode of multiplication 

 among these simpler plants, is made easy by their low de- 

 velopment. Tetraspores arise only where the frond consists 

 of untransformed cells ; gemmae bud out and drop ofi' only 

 where the tissue is comparatively homogeneous. 



Should it be said that this is but another aspect of the 

 antagonism already set forth, since these undeveloped forms 

 are also the smaller forms ; the reply is that though in part 

 true, this is not wholly true. Various marine Algm which 

 propagate asexually, are larger than some Phaenogams which 

 do not thus propagate. The objection that difference of 

 medium vitiates this comparison, is met by the fact tbat it is 

 the same among land -plants themselves. Sundry of the 

 lowly-organized Liverworts that are habitually gemmiparous, 

 exceed in size many flowering plants. And the Ferns show 

 us agamic multiplication occurring in plants which, while 

 they are inferior in complexity of structure, are superior in 

 bulk to a great proportion of annual Endogens and Exogens. 



§ 345. In the ability of the lowly-organized, or almost 

 unorganized, sarcode of a Sponge, to transform itself into 

 multitudes of gemmules, we have an instance of this same 

 direct relation in the animal kingdom. Moreover, the 

 instance yields very distinct proof of an antagonism between 

 development and genesis, independent of the antagonism 

 between growth and genesis ; for the Sponge which thus 

 multiplies itself asexually, as well as sexually, is far larger 

 than hosts of more complex animals which do not multiply 

 asexually. 



Once again may be cited the creature so often brought in 

 evidence, the Hydra, as showing us how rapidity of agamic 

 propagation is associated with inferiority of structure. Its 



