SEVENTEENTH AND EIGHTEENTH CENTURIES XII 

 genera as there are, among the natural vegetable species, flowers (or fructi- 

 fications, as they are termed in these works) differing in number, shape, and 

 position. Classes are defined as a collection of genera that agree in regard to 

 fructification in certain main features. The order, again, is a subdivision of 

 the class which embraces a number of more easily summarized genera. The 

 application of these principles is Linnasus's universally known sexual system, 

 in which the classes are essentially determined according to the number of 

 stamens, and the orders according to the number of pistils. The practical 

 utility of the system is sufficiently evidenced by the fact that it is used to 

 this day in school education, although it was long ago abandoned in actual 

 scientific work. That this system, based as it was on only one organic system, 

 was one-sided, Linnaeus was very well aware, and in several instances he 

 departed from the fundamental principle merely in order to preserve the con- 

 nexion in certain groups which he found to be natural, as, for instance, the 

 classes Didynamia, Tetradynamia, and Gynandria, which, it is true, are 

 characterized by the stamens, but not only by their number, and which com- 

 prise forms that even the system of classification of our own day keeps to- 

 gether. For Linnaeus was fully aware that what should really be striven for 

 in botany was a "natural system": a classification of genera into groups 

 on account of a common similarity, not merely on account of the relations 

 of certain organs. He spent his whole life working out this natural system; 

 the results he achieved will be mentioned later on. 



Linnasus's systematic classification of the animal kingdom cannot be 

 said to have turned out as successfully as his plant system. He divides animals 

 into six classes: (i) Quadrupedia, (2.) Aves, (3) Amphibia, (4) Pisces, (5) In- 

 secta, and (6) Vermes. Quadrupeds are characterized as follows: "the body 

 hairy, four legs, females producing live young, which they suckle"; birds: 

 "the body feathered, two legs, two wings, beak, females laying eggs" — 

 that is to say, purely external characteristics. Linnasus's precursor Ray based 

 his system, as we have seen, essentially upon anatomical characteristics: the 

 structure of the respiratory organs and of the heart; moreover, he differen- 

 tiated, although with faulty characterization, between vertebrates and in- 

 vertebrates; the latter he divides into four groups, while Linnaeus has only 

 two — all details in which Linnasus was undeniably inferior to his pre- 

 cursor. Fishes Linnasus has dealt with entirely in accordance with Artedi's 

 system, which he in fact acknowledges. Of the lower animals the only ones 

 that interest him are the insects. Moreover, Linnaeus has not laid down any 

 general principles for animal classification similar to his Fundamenta botanica. 

 Artedi's " Philosophia kthyologka" might certainly be said to have filled the 

 gap, but the latter's method, as we have already seen, differs not a little 

 from Linnasus's, primarily in the fact that his system is based on the genus 

 and not on the species — and in these circumstances it only remains to show 



