FUNDAMENTAL RELATIONS OF ANIMALS 105 



least not among Radiata, Molliisks, and Articulata, as their respective 

 classes seem to have been introduced simultaneously upon our earth, 

 with perhaps the sole exception of the Insects, which are not known 

 to have existed before the Carboniferous period. Among Vertebrata, 

 however, there appears already a certain coincidence, even within the 

 limits of the classes, between the time of their introduction and the 

 rank their representatives hold in comparison to one another. But 

 upon this point more hereafter. 



It is only within the limits of the different orders of each class that 

 the parallelism between the succession of their representatives in past 

 ages and their respective rank in the present period is decidedly char- 

 acteristic. But if this is true, it must be at the same time obvious to 

 what extent the recognition of this correspondence may be influenced 

 by the state of our knowledge of the true affinities and natural grada- 

 tion of living animals, and that until our classifications have become 

 the correct expression of these natural relations even the most strik- 

 ing coincidence with the succession of their representatives in past 

 ages may be entirely overlooked. On that account it would be pre- 

 sumptuous on my part to pretend that I could illustrate this proposi- 

 tion through the whole animal kingdom, as such an attempt would 

 involve the assertion that I know all these relations, or that where 

 there exists a discrepancy between the classification and the succes- 

 sion of animals the classification must be incorrect, or the relation- 

 ship of the fossils incorrectly appreciated. I shall therefore limit my- 

 self here to a general comparison, which may, however, be sufficient 

 to show that the improvements which have been introduced in our 

 systems upon purely zoological grounds have nevertheless tended to 

 render more apparent the coincidence between the relative standing 

 among living animals and the order of succession of their representa- 

 tives in past ages. I have lately attempted to show that the order of 

 Halcyonoids among Polyps is superior to that of Actinoids; that in 

 this class compound communities constitute a higher degree of de- 

 velopment, when contrasted with the characters and mode of exist- 

 ence of single Polyps, as exhibited by the Actinia; that top-budding 

 is superior to lateral budding; and that the type of Madrepores, with 

 their top-animal, or at least with a definite and limited number of 

 tentacles, is superior to all other Actinoids. If this be so, the preva- 

 lence of Actinoids in older geological formations, to the exclusion of 



