THE PLANARIAN 



Phylum Platyhelminthes Class Turbellaria 



Exercise 1. — Occurrence and General Activities. 



(a) Various kinds of planarians may be found on the under sur- 

 faces of stones, leaves, and other objects in ponds and streams. If 

 pieces of liver are placed in the water, the worms will frequently col- 

 lect upon them and may be washed off into a collecting jar; or the 

 worms maj^ be collected by gently detaching them from the stones on 

 which they are found. Euplanaria novanglise [Planaria maculata) , 

 Euplanaria agilis {P. agilis), and Curtisia joremanii'^ are suitable for 

 the following study. 



(b) Using a handlens and the low-power objective of your micro- 

 scope examine a living planarian in a watch glass of water. How is 

 locomotion accomplished? Turn the animal over with one point of 

 your forceps and observe the movements in righting. Observe the 

 responses to other types of stimuli. Can you discover any evidence 

 of visual sense? Place small bits of crushed snails or other meat near 

 the anterior end and observe what happens; or watch a number of 

 worms in a larger dish after a strip of liver has been dropped upon 

 the bottom. Does it appear that the animals possess a chemical sense? 

 Record your observations, on the righting and feeding, by means of a 

 series of drawings (X 5). 



Exercise 2. — Structure. 



(c) The anterior and posterior ends and the dorsal and ventral 

 surfaces are characteristic for the bilaterally symmetrical animal. 

 Lobelike extensions of the sides of the head are the auricles. What 

 seems to be their function as shown by the feeding experiment? What 

 is the nature of the eyes as seen in the living animal? The tubelike 

 structure that was protruded during feeding is the pharynx; when 

 withdrawn it lies within the pharynx sheath. Where is the mouth? 

 In sexually mature animals find the genital aperture posterior to the 

 mouth. Living specimens will sometimes show the digestive tract. 

 How does its shape justify the name triclad as applied to this order 



^ These names, with the older names in parentheses following them, are ac- 

 cording to the classification of Libbie H. Hyman, TransacLions oj the American 

 Microscopical Society, vol. 50, 1931. 



