PEDICELLATA. GJD 



matter. The TJu-thyce and Sponges nave been joined to this class, though th ir 

 animals have not yet been observed. 



5. Infusoria [Animalcule], the most minute members of the Animal Kingdom, and 

 for the most part microscopic. Some have a very complicated organization, and some 

 appear to be mere particles of animated jelly. [They exist in countless myri 

 principally in stagnant water, and some are so tenacious of life, that, after having 

 been for some time dried to powder, they revive again when moistened.] 



THE FIRST CLASS OF THE RADIATA. 



THE ECHINODERMA.TA. 



These have a well-organised skin ; sometimes a sort of skeleton ; a digestive and a 

 vascular system ; and a sort of radiating nerves. There are two orders: those with 

 feet, or vesicular appendages answering the same purpose, and those without. 



THE FIRST ORDER OF THE ECHINODERMATA. 



I'KDICELL.VTA. 



These have the skin pierced with numerous small holes, through which protrude oylindric 

 Jjntaeula, terminating m suckers. These are extended or retracted bv a humour distinct from 

 that of the intestines, discernible in some of the species, and answer the purpose of feet, by 

 which they perform their locomotion, or adhere to the rocks. Vessels from these continue to 

 unite in a trunk for each row, which trunk terminates near the mouth. The order consists of 

 three very natural families. 



THE FIRST FAMILY OF THE PEDICELLATA,— 



The Astkrias [Star-fish], — 



So called, because the body is generally in the form of a star with five rays. Some, however, as 

 A. discoidea, have the body a pentagon, with straight sides ; others, as A. membranacea, have a re- 

 entering angle in each side ; and others, again, as A. tesselata, have the sides, concave. 



The frame-work of the body is composed of horny pieces, variously arranged. In those which have 



distinct rays, there is a longitudinal groove in the Upper surface of each 

 ray, perforated on both tides, for allowing the action of the feel ; and 



all the surface is covered with pores leading to small tubes which admit 

 water, probably for the purpose of respiration. On the central disc, but 

 toward one tide »( it, then' is a stony plate, and below it ■ canal Oiled 

 with calcareous matter; and it is probable that this is the apparatus by 

 which the hard matter of the bod] is elaborated. There is a lortofvt 

 bratcd osseous column in each ray ; and some of the species have osseous 

 plates, and spines on the sides of the ra\>. Internally, they i 

 Fig. m— A.iciiat. stomach, with two branched eosca extending to each rayj each ray, 



also, contains two ovaries, and it is understood that they propagate by self-impregnation The i 



are easily reproduced, for the central disc and one ray will reproduce all tl there. The mouth, which 



U the only opening to the alimentary organs, is on the under side of the central disc. According to 



Tiedemann, the principal nerve surrounds the mouth, and sends off a filament to each arm. Such are 



