314 STATE OF DEVELOPMENT OF Chap. X. 



these lowly-organized Protozoa ? It is no great difficulty that 

 fresh-water shells, as Prof, Piiillips has urged, have remained 

 almost unaltered from the time when they first ajipeared to 

 the present day ; for these shells will have been subjected to 

 less severe competition than the moUusks inhabiting the more 

 extensive area of the sea with its innumerable inhabitants. 

 Such objections as the above v/ould be fatal to any view which 

 included advance in organization as a necessary contingent. 

 They would likewise be fatal to my view if Foraminifera, for 

 instance, could be proved to have first come into existence, 

 during the Laurentian epoch, or Brachiopods during the Cam- 

 brian formation ; for, in this case, there Avould not have been 

 time sufficient for the development of these organisms up to 

 the standard which they then reached. When once advanced 

 up to any given point, there is no necessity on the theory of 

 natvu'al selection for their further continued progress ; though 

 they will, during each successive age, have to be slightly 

 modified, so as to hold their places in relation to the changing 

 conditions of life. All such objections hinge on the question 

 whether w^e I'eally know how old the world is, and at what 

 periods the various forms of life first appeared ; and this may 

 be disputed. 



The problem whether organization on the whole has ad- 

 vanced is in many ways excessively intricate. The geological 

 record, at all times imperfect, does not extend far enough back, 

 as I believe, to show Avith unmistakable clearness that within 

 the known history of the world organization has largely ad- 

 vanced. Even at the present day, looking to members of the 

 same class, naturalists are not unanimous which forms are to be 

 ranked as highest: thus, some look at the selaceans or sharks, 

 from their approach in some important points of structure to rep- 

 tiles, as the highest fish ; others look at the teleosteans as the 

 highest. The ganoids stand intermediate between the selaceans 

 and teleosteans ; the latter at the present day are largely pre- 

 ponderant in number ; but formerly selaceans and ganoids alone 

 existed ; and in this case, according to the standard of highness 

 chosen, so will it be said that fishes have advanced or retro- 

 graded in organization. To attempt to compare in the scale 

 of highness members of distinct types seemed hopeless : who 

 will decide whether a cuttle-fish be higher tlian a bee — that in- 

 sect which the great Von Baer believed to be " in fact more 

 highly organized than a fish, although upon another type?" 

 In the comjilex struggle for life it is quite credible that cms- 



