I'll YUM I'LATYUKLMISmES 83 



c«iin]);iiis()M of luiisciilar movements of the flatworm and fhosp 

 of Hydra; (7) observations and description of the behavior of 

 tlio tentack's and the anterior end of the animal (hiring locomo- 

 tion, with conclusions; (S) determination of results of stimuliitinn 

 various parts of the animal with a camers-hair brush, especially 

 rejiional difTerence in sensiti\it y. 



At the conclusion of the laboratory period hand in a written 

 report embodying the results of observations upon the structure 

 and behavior of the f^atworm. 



Make a five-inch drawing of the animal from the dorsal side. 

 Show and label eyespots, tentacles, and any other structures 

 observed. 



In a well-fed animal of the white species the digestive canal 

 may be seen clearly outlined in brown. If such an animal is 

 being studied note the oval clear region, the pharyngeal chamber 

 in the center of the body, in which is located an elongate muscular 

 tube, the pharynx. The pharynx can be extended as a proboscis 

 through the mouth opening located on the caudal part of the 

 midventral side. At its cephalic end the pharynx opens into 

 an intestine comprising three main trunks, a median branch 

 extending to the cephalic region, and two lateral branches, one 

 extending caudad on either side of the pharyngeal chamber 

 toward the posterior end of the body. Each of these branches 

 further gives off a large number of irregular lateral extensions. 

 In all probability, the majority of the worms available for 

 study will be of th? dark species (Planaria). Often these may 

 be induced to eat blood or liver if such materials be added to the 

 water in the watch crystal. If a dark-colored worm is being 

 studied, try such a feeding experiment. When the animal begins 

 to eat, a better idea of the structure of the pharynx or proboscis 

 may be gained upon close observation. A little patience while 

 inducing an animal to feed is often rewarded. The general shape 

 of the gastrovascular system of Planaria is similar to that of 

 Procotyla described above. Study a specimen of Planaria pre- 

 pared to show the digestive system. Locate th(> three main 

 divisions and determine the ramifications of each. 



Represent the digestive system in the drawing already made. 

 Flatwornis have well-differentiated nervous, excretory, and 

 reproductive systems, i)ut these are so obscun* that their study is 

 imi)ossible in a living animal. 



