192 LAY SERMONS, ESSAYS, AND REVIEWS. [x. 



simpler, more embryonic, or less differentiated, than the existing 

 forms. 



The COELENTERATA. The Tabulate Corals have existed from 

 the Silurian epoch to the present day, but I am not aware that 

 the ancient Heliolitcs possesses a single mark of a more em 

 bryonic or less differentiated character, or less high organization, 

 than the existing Heliopora. As for the Aporose Corals, in 

 what respect is the Silurian Palceocyclus less highly organized or 

 more embryonic than the modern Fungia, or the Liassic Aporosa 

 than the existing members of the same families ? 



The Mollusca. In what sense is the living Waldheimia less 

 embryonic, or more specialized, than the palaeozoic Spirifer ; or 

 the existing Rhynchonellcc, Cranice, Discincc, Lingulce, than the 

 Silurian species of the same genera ? In what sense can Loligo 

 or Spirula be said to be more specialized, or less embryonic, 

 than Belemnites ; or the modern species of Lamellibranch 

 and Gasteropod genera, than the Silurian species of the same 

 genera ? 



The ANNULOSA. The Carboniferous Insecta and Arachnida 

 are neither less specialized, nor more embryonic, than these that 

 now live, nor are the Liassic Cirripedia and Macrura ; while 

 several of the Brachyura, which appear in the Chalk, belong to 

 existing genera ; and none exhibit either an intermediate, or an 

 embryonic, character. 



The VERTEBRATA. Among fishes I have referred to the 

 Coelacanthini (comprising the genera Ccelacanthus, ffolophagus, 

 Undina, and Macropoma) as affording an example of a persistent 

 type; and it is most remarkable to note the smallness of the 

 differences between any of these fishes (affecting at most the 

 proportions of the body and fins, and the character and sculpture 

 of the scales), notwithstanding their enormous range in time. 

 In all the essentials of its very peculiar structure, the Macropoma 

 of the Chalk is identical with the Ccelacanthus of the Coal. 

 Look at the genus Lcpidotus, again, persisting without a modifica 

 tion of importance from the Liassic to the Eocene formations 

 inclusive. 



