KEY TO PHYLA 19 



statement some one fact (or more) which led yoii to accept that 

 particular step. In so far as possible make these statements in 

 your own words rather than copy the words of the key. For 

 example, the notes on the earthworm would be as follows : 



1 — visible to unaided eye 



6 — bilaterally symmetrical 



15 — segmented 



16 — like a worm, without appendages 



17 — short bristles on segments ; Phylum Annelida 



V-4 — segmented 



6 — setae regularly arranged around segments. Class Chae- 

 topoda, Subclass Oligochaeta. Common name, 

 Earthworm. 



After one or two specimens in the same general group have 

 been identified, the descriptions may be omitted and numbers 

 only given with the names of the Phylum, Class, Order, etc. 

 For example, if a snail and a mussel are both identified the de- 

 scriptions accompanying the numbers of the steps need be given 

 in only one instance leading to the Phylum Mollusca. 



KEY TO THE PHYLA 



1 (2) Animals composed of various organs and tissues, usually 



large enough to be seen without the microscope (the Meta- 

 zoa) 3 



2 (1) Animals consisting of single cells or of groups of cells, 



all of which perform the same functions. Microscopic in 

 size. PHYLUM PROTOZOA (sec page 21) 



3, (6) Body either very irregular in form or radially sym- 

 metrical, but never arranged in spiral form 4 



4 (5) Body more or less indefinite in form. Body wall pierced 

 by numerous small openings (incurrent pores) which lead 

 into internal cavities. The internal cavities also connect 

 with the exterior by one or more larger openings, the oscula. 

 PHYLUM PORiFERA (sec page 21) 



