32 STUDIES OF ANIMAL TYPES 



Find the mouth at the anterior end of the body. Note 

 that it is overhung by a projection, the lip, or prostomium. 



Find the anal aperture, or vent, at the posterior end of 

 the body. 



Make a drawing of the body from a dorsal view. 



C. INTERNAL FEATURES. With sharp scissors, make a 

 shallow incision through the skin, along the median line of 

 the back, the whole length of the body, being very careful 

 not to injure any of the organs beneath. Draw the edges 

 of the cut skin apart and pin down with ribbon pins, 

 beneath water in the dissecting pan. 



Note the delicate partitions, or septa, across the body 

 cavity, dividing it into chambers corresponding to the ring- 

 like divisions of the walls. Note the alimentary canal 

 extending as a straight tube the whole length of the body. 

 It consists of a pharynx, gullet, crop in segments 15 and 16, 

 and a gizzard in segments 17 to 19. The remaining part 

 is the intestine. 



Note three pairs of large white bodies surrounding the 

 gullet. These are the seminal vesicles. Posterior to these 

 are two smaller sacs, the seminal receptacles. 



Note the large blood vessel on the dorsal side of the ali- 

 mentary canal. In segments 7 to 11 will be seen several 

 branches from this blood vessel going around the alimentary 

 canal and meeting a ventral blood vessel below. 



Make a drawing showing these organs. 



Cut the alimentary canal in two at the pharynx and 

 remove the posterior portion. Note the ventral blood 

 vessel beneath. Beneath this note the large white double 

 cord running the whole length of the body. This is the 

 nerve cord. Note in each segment a white knot, or swell- 

 ing, a double ganglion. Trace the nerve cord forward and 



