IV.] MINUTE MODIFICATIONS. 119 



some of the gaps which appear to exist in the series of 

 known forms." 



In addition to the instances brought forward in the 

 second chapter against the minute action of Natural Selec- 

 tion, may be mentioned such structures as the wonderfully 

 folded teeth of the labyrinthodonts. The marvellously com- 

 plex structure of these organs is not merely unaccountable 

 as due to " Natural Selection," but its production by insig- 

 nificant increments of complexity is hardly less difficult to 

 comprehend. 



Similarly the aborted index of the Potto (Perodicticus) 

 is a structure not likely to have been induced by minute 

 changes; while, as to "Natural Selection," the reduction 

 of the fore-finger to a mere rudiment is inexplicable in- 

 deed ! " How this mutilation can have aided in the strug- 



HAND OF THE POTTO (PEBODICTICUS), FEOM LIFE. 



gle for life, we must confess, baffles our conjectures on the 

 subject ; for that any very appreciable gain to the individual 

 can have resulted from the slightly-lessened degree of re- 

 quired nourishment thence resulting (i. e., from the suppres- 

 sion), seems to us to be an almost absurd proposition." 24 



Again, to anticipate somewhat, the great group of 

 whales (Cetacea) was fully developed at the deposition 

 of the Eocene strata. On the other hand, we may pretty 

 safely conclude that these animals were absent as late as 



514 " Anatomy of the Lemuroidea," by James Murie, M. D., and St. 

 George Mivart. Trans. Zool. Soc., March, 1866, p. 91' 



