CLASSIFICATION OF ANIMALS. /OI 



or blood corpuscle, some others without mouths or digestive organs, some 

 have no head ; some, as in the tape-worm, only a so-called head, with 

 suckers or attachments, after which it develops joints, which are at first 

 imperfect, but gradually mature as they are pushed farther away by new- 

 issuing joints. 



Animals, therefore, do not all possess organs, nor is there any common 

 organ by which all animals can be classed. The indispensable in one is 

 absent in another, and while our 

 mouths and digestive apparatus 

 are all important, in other animals 

 suckers and no digestive apparatus 

 at all is quite sufficient. Some 

 have one mouth, some several ; 

 some have mouths and a proboscis 

 to assist them, some only the trunk 

 and no mouth so called at all, 

 as in some insects. 



The organisms which could 

 not be distinguished from vege- 

 tables were termed zoophytes, or Fig. 8 27 .-poiyp idem. 

 plant animals, and, were space available, a comparison might be instituted 

 between the extremes of growth of the animals and plants, from the largest 

 whales to the tiny microscopic protozoa, and from the mould upon jam to 

 the gigantic trees of California, one leaf of which it is said will shelter 

 twenty men from rain. 



Cuvier spent many years in pertecting his systematic arrangements of 

 animals, and this classification, though many rearrangements have been 

 made as modern discovery progressed, may be regarded as the fundamental 

 system of all. Professor Agassiz adopted it with modifications. Professor 

 Nicholson has made a somewhat different arrangement, but essentially there 

 will be found but slight difference between them. We append both these 

 arrangements for comparison : 



AGASSIZ-CUVIER. 



INVERTEBRATA. 



BRANCH I. RADIATA. 



Class 1. Polypi . . 2 orders . Including actinoids and halcyonoids 

 tt \\.-Acalephs . 3 . hydroids, discophorac, ctenophorae. 

 III. Echinoderms . 4 crinoids, asteroids, echinoids. 



BRANCH II. MOLLUSCA. 



Class l.Acephala ? . 4 orders . '^bryoza, brachiopods, tunicata, and lamelli- 



iDranchiata. 

 ., II. Gasteropoda - r .3 ,,,' ,*" ;cjpteropoda, heteropoda, and gasteropoda (pro- 



III. Cephalopoda . 2 tetrabranchiata, and dibranchiata. 1 



