134 WORMS 



water. The worms may be cleaned by placing the contents 

 in a warm normal salt solution. 



(2) Specimens may also be obtained from the lungs or 

 the urinary bladder of the frog if the above source is not 

 convenient. 



(3) To mount Distomum, place the worms between two 

 cover glasses on a slide ; leave in ninety per cent, alcohol for 

 twenty- four hours ; stain faintly in borax - carmine, and 

 mount in balsam. 



Observation. — (i) Examine a living worm under the 

 compound microscope. Do you find the anterior and pos- 

 terior ends? Dorsal and ventral sides? Give reasons for 

 your answers. Is it colored? Why? What gives it its 

 color? Has the surrounding bile a tendency to color it? 

 Describe fully its shape. Does its shape suit its mode of 

 life? 



(2) Has it eyes? Why? Examine the anterior end, 

 Here is situated the anterior oral sucker, in the center of 

 which is the month. Do you find any other suckers ? What 

 are they used for? The mouth leads into a thick muscular 

 pharynx lying just behind. That part of the alimentary 

 tract lying just behind the pharynx is called the esophagus. 

 Trace the remainder of the -alimentary tract. How many 

 branches? Are there any external openings? Compare the 

 alimentary tract with that of the Planaria. 



(3) At the posterior end may be seen the excretory pore 

 and by careful observation the excretory tube may be traced 

 forward from it for a short distance. Draw the entire worm, 

 showing points mentioned. 



State resemblances and differences between Distomum 

 and Planaria. 



