FUNDAMENTAL RELATIONS OF ANIMALS 27 



that their presence upon earth dates from as early a period as any 

 of the three other great types of the animal kingdom, since fishes 

 exist wherever Radiata, Mollusks, and Articulata are found together, 

 and the plan of structure of these four great types constitutes a sys- 

 tem intimately connected in its very essence. Moreover, for the last 

 twenty years every extensive investigation among the oldest fossil- 

 iferous rocks has carried the origin of Vertebrata step by step further 

 back, so that whatever may be the final solution of this vexed ques- 

 tion, so much is already established by innumerable facts, that the 

 idea of a gradual succession of Radiata, Mollusks, Articulata, and 

 Vertebrata is forever out of the question. It is proved beyond doubt 

 that Radiata, Mollusca, and Articulata are everywhere found to- 

 gether in the oldest geological formations and that very early Verte- 

 brata are associated with them, to continue together through all 

 geological ages to the present time. This shows that even in those 

 early days of the existence of our globe, when its surface did not yet 

 present those diversified features which it has exhibited in later 

 periods, and which it exhibits in still greater variety now, animals 

 belonging to all the great types now represented upon earth were 

 simultaneously called into existence. It shows further that unless the 

 physical elements then at work could have devised such plans and 

 impressed them upon the material world as the pattern upon which 

 Nature was to build forever afterwards, no such general relations as 

 exist among all animals of all geological periods, as well as among 

 those now living, could ever have existed. 



This is not all: every class among Radiata, Mollusks, and Articu- 

 lata, is known to have been represented in those earliest days, with 

 the exception of the Acalephs^* and Insects only. It is, therefore, not 

 only the plan of the four great types which must have been adopted 

 then, the manner in which these plans were to be executed, the sys- 

 tems of form under which these structures were to be clothed, even 



** Acalephs [in modern usage coelenterates, e.g., jellyfish] have been found in the 

 Jurassic Limestone of Solenhofen; their absence in other formations may be owing 

 simply to the extraordinary softness of their body. Insects are known as early as the 

 Carboniferous Formation, and may have existed before. — Since the publication of 

 these remarks I have ascertained that Millepora is not a Polyp, but belongs to the 

 Hydroids. It is thus shown that Acalephs have existed in the oldest geological periods, 

 since representatives of the family of Milleporina occur in the Silurian rocks. 



It remains only to be ascertained now whether all the Zoantharia tabulata are as 

 truly Hydroids as the genuine Milleporina or not. 



