14 LABORATORY DIRECTIONS 



words rather than copy the words of the key. For example, the 

 notes on the earthworm would be as follows : 



i visible to unaided eye 



6 bilaterally symmetrical 



15 segmented 



16 like a worm, without appendages 



17 short bristles on segments; Phylum Coelhelminthes, 

 Class Annelida 



V-4 segmented 



6 setae regularly arranged around segments. Subclass 

 Chaetopoda. Order Oligochaetae. 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 descrip- 

 tions 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 Me- 

 tazoa^ ^ 



4.**vcty ^j 



2. (i) Animals consisting of single cells or of a group of 

 cells, all of which perform the same functions. Microscopic in 

 size. PHYLUM PROTOZOA (see page 16) 



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 (see page l6) 



