42 CRUSTACEA 



(b) Size? 



(c) Contents? Open it and see. 



(d) Use of the stomach? 



(5) The Liver — large masses of reddish or brownish mate- 



rial posterior to the stomach. 



(a) Number of lobes? 



(b) Use? 



(6) The Intestines. Trace them from the stomach to 



the vent, in the last segment of the abdomen. 



(a) Straight or coiled? 



(b) Use? 



(7) Diagram or sketch the digestive organs and name them. 



4. The Muscular System. (The Muscles.) 



(1) The white meat. Where do you find it? 



(2) Use to the crayfish? 



(3) Use to man? 



5. The Nervous System. Look for a white cord along the 

 floor of the abdomen. 



(1) Is the cord single or double? 



(2) How many ganglia to a segment? 



(3) How many ganglia in the abdomen? 



(4) How many ganglia in the thorax? 



(5) How many ganglia in all? 



(6) Esophageal ganglia. Trace the nerve cord forward 



until it ends in a larger ganglion about the gullet. 

 To what organs can you trace nerves? 



(7) Sketch plan of nervous sj^stem. 



6. The Special Senses. 



(1) The Eyes. How protected? 



(2) The Ears. 



(a) Ear-sacs. Look for them at the base of the anten- 



nules. 



(b) Size? 



(c) Contents? 

 • (d) Use? 



(3) The Tongue. 



(a) Any present in the mouth? 



(b) Has the crayfish taste?^ 



1 Huxley, p. 115. 



