GROUNDS AND CONSEQUENCES OF EVOLUTION. 343 



plexity and embarrassing synonymy. Mr. Meek described 

 a common Cincinnati fossil as Orthis biforata with four 

 varieties.* Professor Nicholson has taken our old Chcetetes 

 hjcoperdon, a common coral of the Lower Silurian rocks, 

 and enumerated no less than twenty-five distinct variations.! 

 Spin/era disjuncta is a brachiopod abundant in Chau- 

 tauqua county, New York, and neighboring regions, and 

 of this Professor Hall has figured no less than eighteen 

 varieties. J. Of Atrypa reticularis he gives us, similarly, 

 sixteen varieties. These technical names are edifying to 

 the general reader only so far as they demonstrate that 

 great variability has existed in the history of extinct 

 forms, whether we attribute this to hybridity, geograph- 

 ical position or other causes, and furnish additions to the 

 stock of evidence that it is the economy of nature to 

 effect transmutations of species. The sum total of the 

 variational evidence shows us that the derivative origin 

 of types in palaeontological history is a natural possi- 

 bility. We are not in conflict with nature, therefore, in 

 inferring that the terms of the palseontological series sus- 

 tain a consanguineous relation. 



But in the fourth place we -have the embryological 

 evidence. This seems to us to bring all the other evidence 

 to a focus and complete the conviction that the deriva- 

 tive origin of species is a fact. It affords not only a 

 picture of the succession of extinct forms, but it is a 

 picture in which the successive terms are kno-wn to be 



*Meek, Pa'ceontology of Ohio, pi. x. Compare Hall, Palaeontology of New 

 York, i, 133, pi. xxxii D. 



t H. A. Nicholson, Palceonto'ogy of Ohio, ii. 



i J. Hall, Pa'ceontology of New York, iv, pi. xli, xliii. 



J. Hall, Paleontology of New York, pi. li-liii. Compare Whitfield, XIX 

 Rep. N. Y. Regents. 



