98 DARWINISM STATED BY DARWIN HIMSELF. 



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 formerly selaceans and ganoids alone ex- 

 isted ; and in this case, according to the standard of 

 highness chosen, so will it be said that fishes have ad- 

 vanced or retrograded in organization. To attempt to 

 compare members of distinct types in the scale of high- 

 ness 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 organized 

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

 plex struggle for life it is quite credible that crustace- 

 ans, not very high in their own class, might beat ceph- 

 alopods, 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. Besides 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 two periods — though 

 undoubtedly this is one and perhaps the most important 

 element in striking a balance — but we ought to compare 

 all the members, high and low, at the two periods. At 

 an ancient epoch the highest and lowest molluscoidal ani- 

 mals, namely, cephalopods and brachiopods, swarmed in 

 numbers ; at the present time both groups are greatly 

 reduced, while others, intermediate in organization, have 

 largely increased ; consequently some naturalists main- 

 tain that mollusks were formerly more highly developed 

 than at present ; but a stronger case can be made out on 



