56 INVERTEBRATE ZOOLOGY 
CRUSTACEA 
A CLADOCERAN PHYLLOPOD (Daphnia) 
This is a small freshwater crustacean common in lakes and 
pools. It should be studied under the microscope and alive 
if possible. Place several on a slide under a cover-glass and 
draw off enough water to keep them quiet; also observe sev- 
eral in a watch-glass in order to see them from above. The 
body of the animal will be seen to differ in shape from those 
crustaceans already studied. It is but indistinctly segmented, 
and, except the head, is entirely covered by a bivalve shell. 
This shell is the cuticular covering of paired folds of the 
dorsal integument, one fold covering each side of the body. 
Beneath the opening of the valves of the shell appear the 
appendages and the abdomen; on the surface of the shell a mesh- 
work of fine lines can usually be seen. Notice the large, 
median eye; it may often be seen to tremble slightly. The 
shell has a deep, ventral indentation near the base of the 
antenne. 
The first pair of antenne is very small, but may be easily seen 
projecting downward just back of the eye. The second pair of 
antenne is very long and biramous, the two branches being the 
exopodite and endopodite; they are the principal organs of 
locomotion. Just back of the antenne is a large flap, called 
the upper lip, and back of this are the large mandibles. There is 
but a single pair of maxille, and they are so small that they will 
probably not be seen. Four to six pairs of thoracic appendages 
follow, the function of which is probably exclusively respira- 
tory. How many are present in your specimen? Notice 
the leaf-like surface of these appendages (whence the name 
