CLASSIFICATION. 15 



it appears probable that the present classification will never 

 be materially altered. The main features are for the most 

 part defined with clearness. As a result, a number of plans 

 or types of structure are seen in the animal kingdom each 

 plan or type being taken as the standard of comparison for 

 all animals included within its limits. To these ideal pat- 

 terns the tissues more or less regularly conform. If they 

 have the significance by many attributed to them, namely, 

 in each being the expression of a divine idea, it follows that 

 the great principles of classification are fixed. 



These plans are four in number, and are arranged in ac- 

 cordance with the capacity possessed by each for develop- 

 ment, as follows : 



STAR. SAC. RING. VERTEBRA. 



In that large group, the Protozoa,* no plan or plans have 

 yet with certainty been recognized. 



STAR (Radiata). 



A radiate animal is one having its parts disposed around 

 a common central axis, and diverging from it to the periph- 

 ery. (Agassiz.) 



Divided into groups of Ccelenterata and Echinodermata. 



Ccelenterata subdivided into Polypi and Acalephse. 



* PROTOZOA. This term was proposed by Siebold to designate a group of 

 animals, characterized by the various systems of organs not being distinctly 

 separated. (Griffith in Micrograph. Diet.) 



Divided into Rhizopoda, Spongida, and Infusoria. 



Rhizopoda. Essential characters are the gelatinous composition of the 

 body, and the locomotive organs consisting of variable foot-like processes 

 (pseudo-podia). (Griffith, ibid.) 



Spongida. Fixed, aquatic, polymorphous animals; inhaling and imbibing 

 the surrounding element through numerous contractile pores situated on 

 the external surface; conveying it through internal canals or cavities, and 

 ejecting it through appropriate orifices; having an internal flexible or in- 

 flexible skeleton. (Bowerbank.) 



Interior mass occupied with numbers of chambers lined with flagellate 

 cell-like bodies. (Carter.) 



Infusoria. Form variable, fixed or free, round, oval, etc., with integument 

 furnished cither with a ciliated spiral line, or a single flagellum. Interior 

 masa slightly specialized ; a gullet and contractile vesicles making theii 

 appearance. 



