70 ELEMENTARY ZOOLOGY. 



shape? Find the openings into it? Through these the blood enters 

 from the cavity in. which the heart itself lies. Arteries, which always 

 carry blood away from the heart, pass both forward and backward 

 from the heart. A permanent dissection of a lobster in which the 

 arterial system has been injected with a colored mass makes a good 

 supplementary demonstration. 



c. Reproductive Organs. These will be found immediately beneath 

 the sac in which the heart lies, as whitish (male) or yellowish to 

 brown (female) lobed structures. Depending on the sex, there 

 will be found: 



Ovaries or Testes. Form, position, and number of lobes? 



Oviducts or Sperm Ducts. Course, length, and point of outlet? 

 What is the sex of your specimen. Consult the reference texts. 

 Are there any external differences between the sexes ? 



d. Digestive Organs. Remove the sexual organs, nothing more. 

 Liver a pair of yellowish masses anterior and ventral to the 

 reproductive organs. Do these connect with anything? Stomach 

 sketch it in position. Notice its shape. Dissect later, opening 

 it from the ventral surface. Note the anterior and posterior cham- 

 bers, and the grinding apparatus inside. How are the teeth ar- 

 ranged. How do they work in life? 



How is the mouth situated relatively to the stomach? Follow 

 the intestine backward from the stomach to the anus. In what 

 segment is the anal opening? 



Make a sketch of the entire tract from the side, showing in what 

 part of the carapace each region is. 



e. Nervous System. Remove the intestine, cut carefully through 

 the muscles in the midline of the body until the white ventral nerve- 

 chain is uncovered. Follow it forward to the head, cutting away 

 the hard plates that cover it over in the thorax. 



How many swellings (ganglia) in the abdominal region? What 

 is their relation to the segments? Where do nerves arise? What 

 is their probable use? 



Thoracic Ganglia. Number and relation to the appendages? 



Head Ganglia. Look for one under (i. e., posterior to) the gullet, 

 and another (the brain) in front of it. How are these two ganglia 

 connected? Make a diagram of the relation of the nervous system 

 and the digestive tract, from the side. 



f. Excretory Organs. The "green glands" occur in front of the 

 mouth and in the ventral part of the head. They open at the base 

 of the antenna. 



