IOO 



ORGANIC EVOLUTION 



simplicity we have noticed in each case but a single feature 

 of the comparison. 



The embryological repetition of the race history is gen- 

 erally much distorted by secondary modifications which 



FiG. 21. Three stages in the development of a crab (Cancer pagurus). [After HUXLEY.] 



A. A newly hatched larva. B. An older larva. C, D. Much older larvae. In all of these the 

 elongated abdomen is shown. In the two earlier stages some of the legs are seen to be biramous. 



cause all stages in the life history to become more perfectly 

 fitted for their life conditions, but underneath these sec- 

 ondary modifications we can often see indications of the 



