2 RADIATA. 



negative than for their positive characters : hence it wants that unity of composition so 

 well displayed in the sub-kingdoms Mollusca, Articulata, and Vertebrata. Some 

 naturalists have proposed to separate the Radiata into two sections, under the names 

 Aneura and Cgclo-neara, or Acrita and Nemato-neura ; but, unfortunately, the nervous 

 system of only a very few genera of the Cyclo-neura is known, so that, by generalizing 

 too much upon these isolated facts, we are in clanger of reasoning on an error in order 

 to establish a method. 



We include in the sub-kingdom Radiata the six following classes, which may, 

 for the sake of convenience, be subdivided into two sections ; — in the one, the form of the 

 body is more or less globular, sometimes it is symmetrical, often it is irregular or amor- 

 phous, — these form the Globular Radiata. In the second section the body is stellate, 

 and the divisions are arranged in the form of rays around a common centre, — this stellate 

 form can often be shown to consist of a bilateral symmetry. These classes form the 

 Stellate Radiata. The following table exhibits the sections and classes, to which 

 are added the names of typical genera as examples of each : 



1 



Sub-Kingdom. Sections. 



Classes. 



Examples of Genera. 



1. Amorphozoa 



rGlobular Radiata \ 2. Foraminifera 



l 3. Infusoria 

 Radiata. j „ 



/ 4. rOLYPIFERA 



(^Stellate Radiata J 5. Acaleph^! 



[ 6. EcniNODERMATA 



Halichondria, Spongilla, Spongia. 

 Orbitoides, Nummidites, Rotalia. 

 Plcesconia, Dileptus, Paramecium. 

 Alcyordum, Oculina, Meandrina. 

 Medusa, Physalus, Cassiopeeia. 

 Encrinus, Asterias, Echinus. 



Class— ECHINODERMATA. 



The name Echinodermata was given by J. T. Klein, in 1734,* to the shells of Sea- 

 urchins, which were called Echini. Bruguieref subsequently called that class which com- 

 prised the Star-fishes, and the Sea-urchins, Echinodermata. Cuvierj included in his 

 class Echinodermes, with Asterias and Echinus, the Holothuria, animals that are destitute 

 of the prickly skin, of the more typical forms, and have many external affinities with some 

 Mollusca; and subsequently, in his ' Regne Animal,' § he grouped in this class, les Echino- 

 dermes sans pieds, forming the order Sipunculoidea, which connect the Radiata with the 

 Annelidous Articulata. 



* 'Naturalis Dispositio Ecbinodermatum,' Jacobi Theodori Klein, 1734. 



t ' Tableau Encyclope'dique des trois Regnes de la Nature,' 1791. 



X 'Tableau Elementaire de l'Histoire naturelle des Auimaux,' 1798. 



§ 'Regne Animal distribue d'apres son Organisation,' 1834. 



