The great naturalist of the eighteenth century, Carl von Linné, known academically as Carolus Linnæus, was the early associate and close friend of Artedi, and from Artedi he obtained practically all his knowledge of fishes. Linnæus, professor in the University of Upsala and for a time its rector, primarily a botanist, was a man of wonderful erudition, and his great strength lay in his skill in the orderly arrangement of things. In his lifetime, his greatest work, the "Systema Naturæ," passed through twelve editions. In the tenth edition, in 1758, the binomial system of nomenclature was first consistently applied to all animals. For this reason most naturalists use the date of its publication as the beginning of zoological nomenclature, although the English naturalists have generally preferred the more complete twelfth edition, published in 1766. This difference in the recognized starting-point has been often a source of confusion, as in several cases the names of species were needlessly changed by Linnæus and given differently in the twelfth edition. In taxonomy it is not nearly so important that a name be pertinent or even well chosen as that it be stable. In changing his own established names, the father of classification set a bad example to his successors, one which they did not fail to follow. In Linnæus' system (tenth and twelfth editions) all of Artedi's genera were retained save _Lepturus_, which name was changed to _Trichiurus_. The following new genera were added: _Chimæra_, _Tetraodon_, _Diodon_, _Centriscus_, _Pegasus_, _Callionymus_, _Uranoscopus_, _Cepola_, _Mullus_, _Teuthis_, _Loricaria_, _Fistularia_, _Atherina_, _Mormyrus_, _Polynemus_, _Amia_, _Elops_. The classification was finally much altered: the Chondropterygia and Branchiostegi (with _Syngnathus_) being called _Amphibia Nantes_, and divided into two groups--_Spiraculis compositis_ and _Spiraculis solitariis_. The other fishes were more naturally distributed according to the position of the ventral fins into Pisces Apodes, Jugulares, Thoracici, and Abdominales. The Apodes of Linnæus do not form a homogeneous group, as members of various distinct groups have lost their ventral fins in the process of evolution. But the Jugulares, the Thoracici, and the Abdominales must be kept as valid categories in any natural system.