THE HIS inky OF 7s ><>!.< >GY 



brary of such works as had then been written on the subject, and, 

 above all, a deep philosophical and scientific spirit, all combined 

 to produce results not surpassed tor many centuries. We are 

 constantly surprised at the accuracy of many of his statements, 

 some of which have been verified only within recent years ; on 

 the other hand, we need not wonder at the many inaccuracies in 

 his writings, remembering how much credence was then given to 

 tradition, and how laborious must have been the acquisition 

 of facts. We know that his method was correct, for we find him 

 savin-- in his " History of Animals " : "We must not accept a 

 general principle from logic only, but must prove its application 

 to each fact ; for it is in facts that we must seek general princi- 

 ples, and these must always accord with facts. Experience 

 furnishes the particular facts from which induction is the path- 

 wav to general laws." He distinguished some five hundred 

 species of vertebrates, and speaks of a great variety of inverte- 

 brates. He recognized two great groups of animals, those with 

 blood (evaifAa) corresponding to our vertebrates, and those with- 

 out blood (avai/xa) consisting of our invertebrates, for he did not 

 recognize that blood may be colorless. Each of these groups he 

 divided into four, so that his system of classification was as 

 follows : — 



Animals with blood (evaifia) : 



1. Viviparous animals (^wotokovvtu iv olvtols). 



2. Birds (ofjviOe*;). 



3. Oviparous quadrupeds (TtTpairoha. r) unro&u uotokovvtu), including our 



Reptilia and Amphibia. 



4. Fishes (i^ues). 



Animals without blood (dvaifxa) : 



5. Soft animals (/xaAa/aa). such as Cephalopoda. 



6. Soft animals with shells (/xaXaKoaTpaKa). such as Crustacea. 



7. Insects (evTOfJia) . 



8. Animals with shells (oorpaKoSe/Djuara), such as Echinodcrmata and many 



Mollusca. 



He also speaks of other animals, such as jellyfishes and 

 sponges; that he considered the latter as animals is a matter of 

 some surprise, but, on the other hand, his placing the hydroids 

 with plants is a very natural error. Although he advocated the 



