34? STATE OF DEVELOPMENT OP 



Forarninifera, for instance, could be proved to have first come 

 into existence during the Lauren tian epoch, or the above 

 Brachiopods during the Cambrian formation ; for in this case, 

 there would not have been time sufficient for the develop* 

 ment of these organisms up to the standard which they had 

 then reached. When advanced up to any given point, there 

 is no necessity, on the theory of natural selection, for their 

 further continued process ; though they will, during each 

 successive age, have to be slightly modified, so as to hold 

 their places in relation to slight changes in their conditions. 

 The foregoing objections hinge on the question whether we 

 really know how old the world is, and at what period the 

 various forms of life first appeared; and this may well 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 to show with unmistakable clearness that within the 

 known history of the world organization has largely advanced. 

 Even at the present day, looking to members of the same 

 class, naturalists are not unanimous which forms ought to 

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

 sharks, from their approach in some important points of 

 structure to reptiles, 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 preponderant in number ; but for- 

 merly 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 retrograded in organization. 

 To attempt to compare members of distinct types in the 

 scale of highness seems hopeless ; who will decide whether 

 a cuttle-fish be higher than a bee — that insect which the 

 great Von Baer believed to be " in fact more highly organ- 

 ized than a fish, although upon another type " ? In the 

 complex struggle for life it is quite credible that crustaceans, 

 not very high in their own class, might beat cephalopods, 

 the highest mollusks ; and such crustaceans, though not highly 

 developed, would stand very high in the scale of invertebrate 

 animals, if judged by the most decisive of all trials— -the 

 law of battle. Beside these inherent difficulties in deciding 

 which forms are the most advanced in organization, we ought 

 not solely to compare the highest members of a class at any 

 t,wo periods — though undoubtedly this is one and perhaps 



