FOURTH DIVISION. THE RADIATA. 
THESE animals, according to Cuvier, have no mesial planes, but may be 
variously divided into symmetrical parts, radiating {rom one or more axes. 
Their organs of motion, when they have any, are movable spines attached 
to the skin, or flexible papillw, capable of inflation. Some are of distinct 
sexes, some bisexual, and some are produced by buds. They constitute a 
wonderful and mysterious order of life, situated on the outer limit of the 
animal kingdom, between which and the vegetable world seeming to form 
a connecting link. The Radiated Animals are divided into five classes : 
1. Echinodermata (Spiny Skins) ; 2. Hnatozoa (Intestinal Worms), para- 
sites dwelling in the intestines of other animals ; 3. <clealepha (the Sea Net- 
tles) ; 4. Polypi. These were once considered as plants. They are animals 
of a gelatinous substance, with a mouth and digestive organs more or less 
complicated. Many of them live in clusters upon branched or expanded po- 
lypidoms —i. e., polypus houses. Individually, they are very minute, and 
yet they are the most wonderful of architects, constructing vast reefs and 
even islands of hard rock, consisting of salts of lime, cemented by animal 
matter. 5. Infusoria (Animalcule). These are the most minute mem- 
bers of the animal world, and can only be observed by the aid of the micro- 
scope. Many of them are so vitalized, that, after having been for a 
considerable time dried to a powder, they will revive on being moistened. 
CLASS I. THE ECHINODERMATA. 
The animals of this class have a well-organized skin, a digestive system, 
and a kind of radiating nerves. They are arranged in two orders — those 
with feet, or organs -answering the same purpose, constituting the first, and 
those destitute of these appendages, the second. 
Although these animals seem to be the lowest in the order of sentient 
existence, yet a close inspection of their organization shows us many won- 
derful peculiarities, and proves to us once more that Nature has impressed the 
stamp of perfection as well upon her lowest and most simple creatures, as 
upon those that rank highest in the scale. 
(315) 
