THE SEVigN MODERN TYPES. 121 



or Zoophyta) — the sponges, corals, hood-jellies, and comb- 

 jeUies. At the same time, Siebold united the Infusoria with 

 the Rhizopoda, under the name of Protozoa (lowest animals), 

 into a special main division of the animal kingdom. By 

 this the number of animal types was increased to six. It 

 was finally increased to seven by the fact that modern 

 zoologists separated the main division of the articulated 

 animals into two groups : (a) those possessing articulated 

 feet (Arthropoda), corresponding to Linnseus' Insects, 

 namely, the Flies (with six legs), Myriopods, Spiders, and 

 Crustacea ; and (b) the footless Worms (Vermes), or those 

 possessing non-articulated feet. These latter comprise only 

 the real or genuine Worms (ring- worms, round worms, 

 planarian worms, etc.), and therefore in no way correspond 

 with the Worms of Linnaeus, who had included the molluscs, 

 the radiates, and many other lower animals under this name. 



Thus, according to the views of modern zoologists, which 

 are given in aU recent manuals and treatises on zoology, 

 the animal kingdom is composed of seven completely distinct 

 main divisions or types, each of which is distinguished by a 

 characteristic plan of structure peculiar to it, and perfectly 

 distinct from every one of the others. In the natural system 

 of the animal kingdom — which I shall now proceed to explain 

 as its probable pedigree — I shall on the whole agree with 

 this usual division, but not without some modifications, which 

 I consider very important in connection with genealogy, 

 and which are rendered absolutely necessary in consequence 

 of our view as to the history of the development of animals. 



We evidently obtain the greatest amount of information 

 concerning the pedigree of the animal hingdor)i (as well as 

 concerning that of the vegetable kingdom) from comparative 



