EXERCISE X 

 TAXONOMY 



Taxonomy (Gr. taxis = arrangement + nomos = a law) is the 

 arrangement of known facts according to law. As applied to animals, 

 taxonomy has for its object the discovery of the pedigree of every animal 

 from an evolutionary standpoint; that is, its kinship or blood relationship, 

 and consequently its position in the animal series or genealogical tree. 

 The characters used in determining such relationship are the form and 

 structure of the adults, young and embryos, since these most nearly 

 indicate the degree of kinship among organisms. The discovery of homol- 

 ogous structures in two or more animals is regarded as a certain indication 

 of kinship. 



In the work on taxonomy, numerous sketches should be made, but it 

 is left to the student to decide what forms shall be drawn. As aids to 

 memory, these sketches should serve two purposes. First, they should 

 recall those features of animals which place the animals in certain groups; 

 these features are listed in the following exercises under the heading 

 " Characteristics." Second, many animals should be simply remembered 

 as belonging to certain groups, without the necessity of recalling the 

 characteristics which put them in those groups. For this second purpose, 

 the drawings of one phylum or of one class, should be grouped together on 

 consecutive pages. 



Drawings are to be made on note paper, not on the drawing sheets. 



At the end of the exercise on Taxonomy, the student should be able 

 to place any animal studied in its proper group. Be prepared for a test 

 of your ability to do so. 



A. THE PHYLA OF ANIMALS 



All animals have been arranged according to their supposed relation- 

 ships into phyla (Gr. phulon = tribe, race, stock). All members of a 

 single phylum possess certain characteristics in common, and differ 

 in certain of these respects from the members of every other phylum. 

 The principal characteristics of each phylum are listed with illustrative 

 examples, in the following exercises. 



1. Phylum PROTOZOA (Gr. protos = first -f zoon = animal). 



Characteristics. 



la. Unicellular. Examine stained specimens of Amceba. The single 

 nucleus, together with the absence of cell boundaries within the animal 



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