Chap. IV.J ORGANISATION TENDS TO ADVANCE 155 



advanced and be still advancing throughout the world, 

 yet the scale will always present many degrees of per- 

 fection; for the high advancement of certain whole 

 classes, or of certain members of each class, does not at 

 all necessarily lead to the extinction of those groups 

 with which they do not enter into close competition. 

 In some cases, as we shall hereafter see, lowly organised 

 forms appear to have been preserved to the present day, 

 from inhabiting confined or peculiar stations, where 

 they have been subjected to less severe competition, and 

 where their scanty numbers have retarded the chance 

 of favourable variations arising. 



Finally', I beheve that many lowly organised forms 

 now exist throughout the world, from various causes. 

 In some cases variations or individual differences of a 

 favourable nature may never have arisen for natural 

 selection to act on and accumulate. In no case, prob- 

 ably, has time sufficed for the utmost possible amount of 

 development. In some few cases there has been what 

 we must call retrogression of organisation. But the 

 main cause lies in the fact that under very simple con- 

 ditions of life a high organisation would be of no service, 

 — possibly would be of actual disservice, as being of a 

 more delicate nature, and more liable to be put out of 

 order and injured. 



Looking to the first dawn of life, when all organic 

 beings, as we may believe, presented the simplest struc- 

 ture, how, it has been asked, could the first steps in the 

 advancement or differentiation of parts have arisen? 

 Mr. Herbert Spencer would probably answer that, as 

 soon as simple unicelhilar organism came by growth 

 or division to be compounded of several cells, or became 

 attached to any supporting surface, his law "that 



