120 THE HISTORY OF CREATION. 
myriopods, spiders, and crustacea, but besides these, a large 
number of the worms, especially the rmged worms. The 
third main division comprises the molluscous animals 
(Mollusca)—slugs, snails, mussels, and some kindred groups. 
Finally, the fourth and last circle of the animal kingdom 
comprises the various radiated animals (Radiata), which at 
first sight differ from the three preceding types by their 
radiated, flower-like form of body. For while the bodies of 
molluscs, articulated animals, and vertebrated animals consist 
of two symmetrical lateral halves—of two counterparts or 
antimera, of which the one is the mirror of the other—the 
bodies of the so-called radiated animals are composed of 
more than two, generally of four, five, or six counterparts 
grouped round a common central axis,as in the case of a 
flower. However striking this difference may seem at first, 
it is, in reality, a very subordinate one, and the radial form 
has by no means the same importance in all “radiated 
animals.” 
The establishment of these natural main groups or types of 
the animal kingdom by Bar and Cuvier was the greatest 
advance in the classification of animals since the time of 
Linneus. The three groups of vertebrated animals, articu- 
lated animals, and molluscs are so much in accordance with 
nature that they are retained, even at the present day, little 
altered in extent. But a more accurate knowledge soon 
showed the utterly unnatural character of the group of the 
radiated animals. Leuckart, in 1848, first poimted out that 
two perfectly distinct types were confounded under the 
name, namely, the Star-fishes (Echinoderma)—the sea-stars, 
lily encrinites, sea-urchins, and sea-cucumbers ; and, on the 
other hand, the Animal-plants, or Zoophytes (Ccelenterata, 
