18 Zoological Systems. 



wards the vertebrata, as towards the culminating type of 

 animality. Others admit many series, whether parallel, or 

 diverging and variously combined ; each according to his own 

 views. Finally, there are others who consider the great 

 divisions of the animal kingdom, as well as the particular 

 classes, as equivalent groups, which do not admit of grada- 

 tion, and each of which represents a separate mode of exist- 

 ence, as perfect in its sphere as any other group whatever. 

 According to this mode of viewing the subject, there can be 

 no gradations in nature. 



It is evident that if these systems are true, they ought to 

 be confirmed by the study of fossil animals, and their mode 

 of existence in anterior creations. Now none of these modes 

 of considering the subject appears to me to answer to the 

 primitive order of things, such as the study of fossils has 

 enabled me to observe in the relations which have existed 

 from the most ancient times between all the classes of the 

 animal kingdom. 



The first important fact opposed to these systems being 

 regarded as a true and complete expression of the natural 

 relations which connect organized beings with each other, is 

 the certainty which we have acquired, for about a quarter of 

 a century, that the animals now living on the surface of the 

 globe constitute but a small proportion of those which for- 

 merly inhabited it. And if this be the case, must not any 

 attempt to unite all animals in the same plan, in classifica-. 

 tions founded only on the study of living species, be extremely 

 arbitrary, especially since it has been demonstrated that the 

 appearance and disappearance of extinct types correspond 

 to determinate epochs 1 Accordingly, the necessity of a more 

 complete system is felt more strongly every day, in propor- 

 tion as we discover a greater number of extinct genera, fami- 

 lies, and even entire orders. The systems which regard the 

 animal kingdom, viewed as a whole, as produced all at the 

 same time, as composed of contemporaneous types, and ca- 

 pable of being placed in the same rank, with regard to their 

 natural value, evidently do violence to primitive relations, and 

 to the chronological order of creation. Before proceeding to 

 classify organized beings, it is neccessary, in our day, to 



