118 . The American Naturalist. [February, 
THE CLASSIFICATION OF THE ARTHROPODA. 
By J. S. KINGSLEY. 
_ In the concluding section of my paper on the Embryology 
of Limulus (93), I expressed my views upon the classification 
of the Arthropods. The following is to be regarded as an ex- 
pansion of the remarks I then made, with the inclusion of 
some matter not then available. 
Since the days of von Siebold (’46), the naturalness of the 
group of Arthropoda has been almost universally recognized, 
only a few, like the present writer (’83) and von Kennel in his 
recent text-book of Zoology (93), appearing to doubt the homo- 
geneity of the division. On the other hand, the way 1 
which the Arthropoda should be subdivided has been very 
differently regarded by different authors. Space will not per 
mit an extended résumé of the growth of our knowledge, but 
it is fair to say that almost every person treating of the subject 
has added materially to the basis for a natural classification, 
either by the discovery of new facts or by throwing new lig ; 
upon facts known before. At present, the great majority of 
naturalists divide the Arthropod phylum into two groups n 
sub-phyla, which, however named, are essentially Branchiata 
and Tracheata, the former embracing the Trilobites, Euryp- 
terids, Hemiaspids and Xiphosures, along with the true Crus- 
tacea; the latter containing the Onychophora (Peripatus) 
Myriapods, Hexapods and Arachnids. 
Yet this division is not universally accepted, and a few ya 
ago, Professor E. Ray Lankester, following out the earlier sug- 
gestion of Strauss-Dürckheim and the later one of the young? 5 
van Beneden (’71), demonstrated that the affinities of Limulus 
were with the the Arachnids rather than with the Crustacea. 
This epoch-making paper—“ Limulus an Arachnid ”—™ 
form the basis of all farther studies of Arthropod taxonomy 
since it logically follows from his conclusions that the p 
tions made between Branchiata and Tracheata are physiologr 
