MOLLUSCA. RADIATA. 



Star Fish. 



Botr\ llus Stellatus. a Group of four Botrylluses 

 attached to the base of an Ascidia Intestinalis. 

 b Botryllus magnified. 



Ascidia Australia. A External aspect 

 v Internal structure. 



translucent membrane. Most of this class are generally attached to solid bodies, or to each other. In the 

 latter case several individuals, each being distinct, are surrounded by a common membrane. The tunic is 

 always provided with two apertures, one for the entrance and the other for the exit of water, which sup- 

 plies the creature's food, besides oxygenating its blood. The Ascidia Australis affords an example of the 

 Tunicata. 



The Stellated Botryllus (Botryllus Stella tus) affords another specimen of the Tunicata. 

 the Mediterranean. 



It is found in 



The reader will recollect that the animal kingdom of which we are treating, comprises four great sub- 

 kingdoms, of which we have already examined three, viz. Vertebrata, Articulata, and Mollusca. We now 

 come to the last and lowest form of animal life, the sub-kingdom, Radiata. 



The Radiata, like the Mollusca, comprises a vast number of classes and species, differing more or less 

 from each other, yet exhibiting with greater or less distinctness certain common marks. They take their 

 name from having a form approximating to the circular, a mouth in the centre of one of the surfaces, and 

 something like a ray-like disposition of the parts around the mouth. It were difficult, if not impossible, to 

 specify any other distinctive mark applicable to all of them. We therefore proceed at once to touch briefly od 

 the several classes. 



The class, Polygastrica, includes the greater part of the animalcules — those minute beings, which, so far 

 as concerns man, may be called the creation of the microscope. It is now known, that these creatures 

 abound in every drop of stagnant water, and even in the whole mass of the ocean. Neither need we say 

 stagnant water, for all unfiltered water will be found swarming with this species of animal life. So beyond 

 enumeration are the varieties of these animals, and so minute are the peculiarities distinguishing each 

 variety from the other, that without attempting to specify marks common to all, we shall content ourselves 

 with presenting a few specimens. 



The class, Echinodermata, takes its name from the prickly skin, with which most of its species are fur- 

 nished. The Star Fish, and Sea Urchin are examples of it. Some of the species, however, forming the 



Various forms of Animalcules (Potygastrica.) 



Sea Anemone. 



Sea Urchin 

 (380) 



