34 STRUCTURAL AND SYSTEMATIC ZOOLOGY 



Platyhelminthes and Nemathelminthes 

 Tapeworm, or Trichina 



Material. Alcoholic specimens of the former and 

 microscopic preparations of the latter may be studied 

 and attention called to their complicated developmental 

 history, and their pathologic significance (Figs. 37, 38, 39). 



Echinodermata 



Starfish 



Aquarium Study- If live specimens can be obtained, 

 study their mode of locomotion ; the flexibility of the 

 rays and the body; the movement of the spines along 

 the grooves, around the mouth opening, and at the 

 tip of the ray where the eye is located ; note the sensi- 

 tiveness of the various parts, particularly of the tube 

 feet* and of the branchiae ; note also that the numerous 

 tube feet move as though regulated or coordinated by 

 some governing power, their movements being thus 

 directed toward the attainment of some definite end 

 instead of being at random. Examine a number of 

 specimens and look for variations in the size of the 

 rays. These will show the power of regenerating lost 

 parts, which the starfish possesses to a high degree. 



Structure. Study the position and arrangement of 

 all external parts, the spines, tube feet, eyes, branchiae, 

 madreporic body, peristome, the radial nerve in the 

 roof of each groove. Remove the upper half of the 

 outer " shell " and note the internal organs : the digestive 

 system consisting of the stomach and digestive glands ; 

 the internal parts of the water-vascular system, the water 

 sacs and the " stone canal" ; the reproductive glands; 

 note the radial plan of structure (Figs. 46, 323, 330). 



Exhibit a series of eggs, showing different stages 

 of segmentation, also the larval forms of the starfish. 



