LOBSTER OR CRAYFISH 163 



E. — The Excretory System. 



Lying in the lower side of the head will be found 



a. The "green glands" or kidneys. — What is their 

 position with reference to the mouth ? How do 

 they compare in size and color with the digestive 

 glands ? Is there any similarity in the general 

 structure of the two kinds of gland ? 



Leading from the green glands to the base of 

 the antennae find 



h. The ureters. ^ — What is their shape? Length? 

 Pass a bristle into the opening in the tubercle on 

 the base of the antenna. Does the bristle enter 

 a ureter ? 



F. — The Reproductive System. 

 In the male find 



a. The testes (in the lobster, two tubular organs ex- 

 tending from the lateral angles of the stomach 

 back into the abdomen ; in the crayfish, an organ 

 bilobed anteriorly, but with a single lobe poste- 

 riorly). — How far back do they extend ? What 

 is their color? What is their position with re- 

 gard to the intestine ? To the heart ? What 

 holds them in position? Are the two organs 

 connected at any point ? 



Cut into one of the testes of a recently killed 

 specimen, place a drop of the contained fiuid upon 

 a slide, and examine with a high power. Exam- 

 ine the shape and general appearance of the 

 sperm -cells or spermatozoa. Do they move? 

 Draw some of these cells. 



Leading from the testes find two tubes. 



