No. 554] 



AD APT A TIOX Til HOUGH SKLFA ' T10X 



69 



Neumayr's well-remembered figures of fossil Palud- 

 inas from Slavonian lake deposits show an increasing 

 rugosity of shell and irregularity of aperture, but the 

 separate steps of this change could hardly have been 

 of selection value and have occurred under the con- 

 trol of natural selection. One is irresistibly drawn to 

 believe that there was in these Paludinas an internal 

 tendency to mutate from generation to generation toward 

 increasing rugosity of the shell and increasing irregu- 

 larity of its aperture. 



Similar trends in the development of limb and tooth 

 structure of the horse were long ago emphasized by 

 American paleontologists. There is no conceivable utility 

 in the modified shell form of the Pahulina, and. in the 

 case of the horse, the wonder is that the race has not long 

 ago been exterminated. Among the Cephalopoda are 

 some forms which show most complex patterns of the 

 partitions. There are complete intergrading stages 

 shown in the known species between simple suture lines 

 and the most fantastically fimbriated. There seems here, 

 again, to be evidence of a trend toward increasing convo- 

 lution of the sutures, rather than evidence of the appear- 

 ance of a useful character and its increase by successive 

 steps each of selection value. In a somewhat similar way, 

 over-ornamentation and bizarre character developed in 

 the Trilobites by steps which can hardly be imagined 

 useful. Many such examples might be cited. 2 



It may seem that I am arguing against the importance 

 of natural selection, but I think I am not, and for this 

 reason: the very trends, of whose existence I think we 

 have good evidence, are themselves subject to natural 

 selection, and if they are in hurtful directions, they will 

 ultimately cause the extermination of the species exhibit- 

 ing them. I very much doubt if such a monstrosity as 

 the horse could long persist, except for man 's aid, for it 



