31 



Mammalian limbs. 



Baptanodon. 



Chelydra. 



Evolution of ungulate limb, 



Zygapophyses, 



Teeth. 



The brain. 



Evolution of Planorbis at Steinheim, 



Strombiis in Florida. 



4. The evidence from Embryology. 



(Romanes, pp, 147-154.) 



Recapitulation of geological stages in ontogeny. 



Antlers of the stag. 



Tails of fishes, 



This also a recapitulation of the classification 

 of existing forms. 



Law that higher forms pass through ontogenetic 

 stages corresponding to lower forms well shown 

 by Scyphomedusae. 



The earlier stages in ontogeny are common to 

 the largest groups while the latter stages are 

 restricted to smaller and smaller groups. 



Egg not found in Protozoa, but is the protozoan 

 stage in all higher groups. 



Gastrula present in higher coelenterates and is 

 coelenterate stage in all higher forms. 



Early stages of echinoderm larva of one type for 

 whole group. This developes into a different 

 type of larva for each sub-group. 



The nauplius (Korschelt and Heider.) 



Special larval forms of groups of Crustacea. 



