THE CRAYFISH. 33 



2. Under the heart, and projecting in front of it, are the 

 reproductive organs : in the female, the yellowish 

 ovaries, in which the spherical eggs may be distin- 

 guished; in the male, the whitish testis occupies a 

 corresponding position. The ovary on each side sends 

 downward a tube, the oviduct, or egg-tube, to the 

 first segment of the third thoracic leg, where it opens 

 externally. The testis has a much longer, coiled 

 white tube, which opens on the first segment of the 

 hindmost thoracic leg. 



3. Carefully cut away the roof of the head. The space 

 within the head is almost completely occupied by 

 the stomach, a roundish sac, with a thin wall, in 

 which is a hard framework. Gently scrape away 

 the soft tissues around the stomach, and examine it 

 closely. Observe the narrow gullet or esophagus 



' leading from the mouth to the stomach. 



4. Along the sides of the posterior end of the stomach 

 and the anterior end of the intestine lie large reddish 

 masses, the liver. Pick one of these masses to pieces 

 to learn its structure. Find the duct leading from 

 each liver into the intestine. 



5. Observe the white muscles which extend forward 

 from the abdomen along each side of the body 

 cavity. 



b. Beginning at the front end of the abdomen, cut with 

 scissors through the roof of the abdomen to the 

 telson, on each side. Seizing the fore part of this 

 roof with the forceps, carefully lift it and turn it 

 backward. A thin layer of white muscle may adhere 

 to it, or may remain connected with the organs in 

 the abdomen. This is made up of the muscles that 



