270 ZOOLOGY. 



With a pair of fine, sharp pointed scissors make a longitudinal 

 incision into the integument of the abdomen near each side. 

 Gradually and carefully remove the skin between the cuts from 

 behind forward. Look for the heart, a long, thin-walled, mid- 

 dorsal vessel, which if not removed with the skin may be seen 

 just beneath it. Unroof both the abdomen and thorax. Note the 

 exposed muscles of the thorax, also the whitish fat bodies next 

 the body wall. 



1. Trachea. If the specimen is freshly killed the tracheae will be 

 rilled with air and will show as white, glistening tubes. Seek their 

 connection with the spiracles, and note their ramification and 

 unions in the body. Isolate some of the smaller branches and study 

 under the microscope. Prove that they are tubes. How kept open? 



2. Reproductive Organs. (These are much more difficult in the 



male.) 



Ovaries: In how many masses? Notice the subdivisions of the 

 ovaries. These contain the eggs and communicate by means of 

 an oviduct with the outside. In what segment? Examine an 

 ovum with the microscope. Mash, and notice the yolk. 



3. How do the muscles of the thoracic region differ from those in 

 the abdominal? Are the fibres plain or striate? 



4.- Digestive Tube. 



Dissect forward into the head, and press the other organs aside so 

 that the course of the tract may be revealed. It consists of 

 the following parts, which should be identified. 

 Mouth. 



(Esophagus; size and course. 



Crop (an enlargement of the oesophagus) ; shape, position. 

 Stomach : character and extent. (At the anterior end is a ring 

 of tubular appendages which are glandular in function, the 

 gastric caeca; at the posterior end it is limited by a circle of 

 fine tubes Malpighian tubules which are excretory.) 

 Intestine; length, course and size. 

 Anal opening; position. 



Make drawing of digestive tract from side view, showing in outline 

 the body regions and the relation of the portions of the tract to 

 these. 

 5. Nervous System. (Remove the alimentary tube and examine the 



floor of the abdominal cavity.) 

 Ventral nerve cord. Is it single or double? 



Ganglia; number, and relation to the segments. 

 Nerves ; origin and distribution. 

 Trace forward into the thorax and head. 



Ganglia; number and position. How connected? Is there any 



portion dorsal to the digestive tract (brain) ? 

 Nerves. 



