32O Doubts Relative to the Epochal and 



etc. different groups and species pass through a long suc- 

 cession of strata, yet the individuals of each stratum have a 

 sufficiently defined marking and proportions to determine 

 which stratum produced them, and if found out of their 

 proper order, receive from the experienced palaeontologist the 

 condemnation of being derived, and not properly indigenous 

 to that formation. 



Without, therefore, any laboured attempt to prove that 

 which geologists already grant, that each stratum contains 

 its own organic remains, within certain geographical areas ; 

 or attempting to show that organic remains, though not in a 

 regular gradational order, as a whole observe an ascending 

 or progressive order of organization, it will be only necessary 

 to observe that, from the lower Silurian and Laurentian on- 

 wards to the highest of the secondary rocks, or the upper 

 Cretaceous formations, and onwards through the Tertiaries, 

 we have successive forms of algae, confervse, mosses, ferns, 

 monocotyledons, as palms and canes, or the order of cyca- 

 deoidese and coniferas, with the still higher dicotyledons per- 

 taining to the vegetable kingdom. And in the animal king- 

 dom innumerable genera and species now extinct and 

 unrepresented, with genera fully preserved in the existing 

 fauna, but whose precise individual species or family remain 

 distinct from the lowest of the rhizopods or protozoae to the 

 higher forms of mammalia. 



The only general exception to this distinction in the indi- 

 vidual species is in the lower forms of protozoic life, where, 

 from the variety and close proximal forms different species 

 undergo from different degrees of pressure, heat, and perhaps 

 light to which they have been subjected, distinct species and 

 genera are occasionally almost indistinguishable from each 

 other, as has been shown in the beautiful monographs by 

 Messrs. Parker and Jones, and the more elaborate work, 

 issued by the Ray Society, upon the Foraminiferae, by the 



