136 GENERAL EVOLUTION. 



Molluscs had reached a great pre-emmeuce. It is difficult to be 

 sure whether the Protozoa had a greater numerical extent in the 

 earliest periods than now, but there can be no doubt that the 

 Coelenterata (corals) and Echinoderms (crinoids) greatly exceeded 

 their present bounds in Paleozoic time, so that those at present 

 existing are but a feeble remnant. If we examine the sub- 

 divisions known as classes, evidence of the nature of the succes- 

 sion of creation is still more conclusive. The most poljp-like of 

 the Molluscs (Brachiopoda) constituted the great mass of its repre- 

 sentatives during Paleozoic time. Among Vertebrates the fishes 

 appear first, and had their greatest development in size and num- 

 bers during the earliest periods of the existence of the division. 

 Batrachia were much the largest and most important of land ani- 

 mals during the Carboniferous period, while the higher Verte- 

 brates were unknown. The later Mesozoic j^eriods saw the reign 

 of reptiles, whose position in structural develojoment has been 

 already stated. Finally, the most perfect, the mammal, came 

 upon the scene, and in his humblest rej^resentatives. In Tertiary 

 times Mammalia supplanted the reptiles entirely. 



Thus the structural relations, the embryonic characters, and 

 the successive appearance in time of animals coincide. The same 

 is very probably true of plants. 



That the existing state of the geological record of organic 

 types should be regarded as anything but a fragment is, from 

 our standpoint, quite preposterous. And, more, it may be as- 

 sumed with safety that when completed it will furnish us with 

 a series of regular successions, with but slight and regular in- 

 terruptions, if any, from the species which represented the sim- 

 plest beginnings of life at the dawn of creation, to those which 

 have displayed complication and power in later or in the present 

 periods. 



For the labors of the paleontologist are daily bringing to light 

 structures intermediate between those never before so connected, 

 and thus creating lines of succession where before were only in- 

 terruptions. Many such instances might be adduced : two might 

 be selected as examiDles from American paleontology ; * i. e. , the 



* Prof. Huxley, in the last anniversary lecture before the Geological Society 

 of London, recalls his opinion, enunciated in 1862, that "the positively-ascertained 

 truths of Paleontology " negative " the doctrines of progressive modification, which 

 suppose that modification to have taken place by a necessary progress from more to 

 less embryonic forms, from more to less generalized types, within the limits of the 



