DEVELOPMENT AND GENESIS. 441 



flther. An insect, passing from its lowly- organized cater- 

 pillar-stage into that of chrysalis, is afterwards a week, a fort- 

 night, or a longer period in completing its structure : the re- 

 commencement of genesis being by so much postponed, and 

 the rate of multiplication therefore diminished. Further, that 

 re- arrangement of substance which development implies, en- 

 tails expenditure. The chrysalis loses weight in the course 

 of its transformation ; and that its loss is not loss of water 

 only, may be inferred from the fact that it respires, and that 

 respiration indicates consumption. Clearly the matter con- 

 sumed, is, other things equal, a deduction from the surplus 

 that may go to reproduction. Yet again, the 



more widely and completely an organic mass becomes diffe- 

 rentiated, the smaller the portion of it which retains the re- 

 latively-undifferentiated state that admits of being moulded 

 into new individuals, or the germs of them. Protoplasm 

 which has become specialized tissue, cannot be again 

 generalized, and afterwards transformed into something else ; 

 and hence the progress of structure in an organism, by 

 diminishing the unstructured part, diminishes the amount 

 available for making offspring. 



It is true that higher structure, like greater growth, may 

 insure to a species advantages that eventually further its mul- 

 tiplication may give it access to larger supplies of food, or 

 enable it to obtain food more economically ; and we shall 

 hereafter see how the inverse variation we are considering is 

 thus qualified. But here we are concerned only with the 

 necessary and direct effects ; not with those that are con- 

 tingent and remote. These necessary and direct effects wo 

 will now look at as exemplified. 



344. Speaking generally, the simpler plants propagate 

 both sexually and asexually ; and, speaking comparatively, 

 1 he complex plants propagate only sexually: their asexual 

 propagation is usually incomplete produces a united aggre- 

 'gate of individuals instead of numerous distinct individuals. 



