THE PALEONTOLOGICAL RECORDS 301 



succulent marshy vegetable food for dry grassy materials, etc.). 

 The full phylogeny would express all the other anatomical 

 characters involved in the processes of transformism, but we only 

 know the skeletal ones (including the teeth) from direct evidence. 

 As another example we may take the phylogeny of the modern, 

 dominant Teleostean fishes. 



r.-i 1-1 ^1 ' Elasmobranchii 

 / Chonarichthves — , yj , , ,• 



T^ . . . ■ < Jrlolocephali 



rnniitive 1 / a r j t" 1 ^ • 



r,., • T- t- -, /rr« 1 ^ • ' Aloaern i eleostei 



bilurian rishes f i eleostomi — .^.^ , <c /-. -j >> 



L-i ^ • u u ' ^ Modern Ganoids 



VOsteichthyes — 



vDipnoi 



and so on. 



And reference to the records of paleontology will give series of 

 major sequences that fit into this scheme. 



Phylogenies, then, we assume to show the evolutionary histories 

 of races of organisms — the directions and results of processes of 

 transformism. 



Paleontological records are used in two ways : (i) A fossil is 

 the material from which we deduce the types of structure of an 

 extinct animal so that we can include the latter in our classifica- 

 tions. A rational classification thus includes past, as w^ell as 

 present life. (The above classification of Fishes, if written out 

 in full, would contain many groups that are now extinct.) In 

 such a scheme the extinct forms fill up obvious gaps in the 

 classification of living ones. 



The paleontological records, besides filling up these gaps, date 

 classifications : thus morphology leads us to infer that Birds and 

 Reptiles are more closely allied than Birds and Mammals or 

 Reptiles and Mammals. And the fossil Bird, Archeopteryx, shows 

 Reptilian characters more prominently than any other living or 

 fossil Bird. And Archeopteryx is the oldest known fossil Bird. 



In the main phylogenies are based on the comparisons of 

 structure in living races of organisms. Because of the exceptional 

 and accidental nature of the process of fossilization it is the 

 case that paleontological sequences, such as are mentioned above, 

 are rather rare. Undoubtedly there are deficiencies in the record 

 due to actual destructions of stratified rocks with their included 

 fossils. But so far as they go, the fossil records enable us to infer 

 that the logical order exhibited by phylogenies founded on 

 structures of living races of organisms is also a time-order. 



