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 What color has the crawfish? Is this color of any use to the crawfish?

Make out the two distinct regions or divisions of the body (Fig. 81). The anterior (front) region is called the head-chest or cephalothorax, and the posterior (rear) region is called the tail. Which region is larger? Why? Which is flexible? Why?

Is the covering of the body hard or soft? What is the advantage of such a covering? What are its disadvantages? How is the covering modified at the joints to permit motion?

Tail.—How many joints, or segments, on the tail? (Figs. 81, 83.) Does the hard covering of each segment slip under or over the segment behind it when the abdomen is straight? Does this lessen friction while swimming forward?

with swimmeret.

Is there a pair of swimmerets to each segment of the abdomen? (Figs. 82, 86.) Notice that each swimmeret has a main stalk (protopod), an outer branch (exopod), and an inner branch (endopod) (Fig. 84). Are the stalk and the branches each in one piece or jointed? The middle part of the tail fin is called the telson. By finding the position of the vent, decide whether the food tube goes into the telson (Fig. 82). Should it be called an abdominal segment. Are the side pieces of the tail fin attached to the telson or to the sixth segment? Do these side pieces correspond