ARRANGEMENT AND CLASSIFICATION 63 



brate animals. Some recorded their anatomy with greater or less 

 fulness, while others gave an accurate and detailed history of the 

 metamorphoses and habits of a great number of these animals ; as a 

 result of their valuable observations, we have become acquainted 

 with many facts of the greatest importance. 



At length Linnaeus, a man of high genius and one of the greatest 

 of naturahsts, after having marshalled the facts and taught us the 

 necessity for great accuracy in the determination of all kinds of 

 characters, gave us the following classification for animals. 



He divided known animals into six classes, based upon three stages 

 or characters of organisation. 



Classification of Animals, established by Linn^us. 

 Classes. \ First Stage. 



I. Mammals. V Heart with two ventricles : blood red and 



II. Birds. J warm. 



III. Amphibians (EeptUes). I Second Stage. 



IV. Kshes. / Heart with one ventricle : blood red and cold. 

 V. Insects. \ Third Stage. 



VT. Worms. / A cold serum (in place of blood). 



Except for the inversion displayed by this arrangement as by all 

 others the four first divisions proposed are now definitely estabhshed, 

 and will henceforth always obtain the assent of zoologists as to their 

 position in the general series. For this we are primarily indebted to 

 the illustrious Swedish naturalist. 



The case is different with regard to the two final divisions of the 

 arrangement in question ; they are wrong and very badly disposed. 

 Since they comprise the greater number of known animals of the 

 most varied characters, they should be more numerous. Hence it 

 has been necessary to re-constitute them and substitute others. 



We have seen that Linnaeus, and the naturalists who succeeded him, 

 gave very little attention to the necessity for increasing the number 

 of divisions among animals which have a cold serum in place of blood 

 (invertebrate animals), and whose characters and organisation are so 

 greatly varied. Hence they have divided these mmierous animals 

 into two classes only, viz. insects and worms ; so that everything 

 which was not regarded as an insect, that is to say all invertebrate 

 animals that have not jointed legs, were referred without exception 

 to the class of worms. They placed the class of insects after the fishes, 

 and the worms after the insects. According to this arrangement of 

 Linnseus, the worms constituted the final class of the animal kingdom^ 



These two classes are still maintained in the same order in all the 

 editions of the Sy sterna Naturae pubhshed subsequently to Linnaeus. 

 The essential vice of this arrangement, as regards the natural order of 



