INVERTEBRATE ZOOLOGY. 61 



do Amoebae eat V Can you find a circular pinkish object that appears and dis- 

 appears ? This is the contractile vacuole. Can you see the nucleus V This is 

 also circular and like the surrounding protoplasm. l)ut more refractive. 



3. &• In case of most shelled forms, the protoplasm cannot be well ob- 

 served through the thick walls of the shell. In these, watch the large aper- 

 tvu-e of the shell and l(x)k for pseudopodia which may project from it, often 

 for some distance (nearly the longer diameter of the shell). These may be 

 finger-like (Difflngia) or exceedingly delicate and fihunentons (Englyjjha). In 

 some delicate shells (Hyalosphenia. Cyjihoderia) the interior protoplasm may 

 be seen, connected with the shell Ijy tapering threads. Encysted forms may 

 be observed without pseudopodia, and the protoplasm in the form of a sphere 

 within the shell. 



3, <'• Keep watch for reproducing Rhizopods. In the shelled forms the 

 new one grows from the ai)erture of the shell. When fully formed one sees 

 a pair of shells placed mouth to mouth. 



4, (This experiment is not an essential one. but valuable for comparison). 

 The '• white blood corpuscles" or Leucocytes are amoeboid cells with nucleus 

 and pseudopodia. Tliey occur in the blood and lymph as well as in the saliva 

 and in the alimentarj' canal. They ma.y be studied for comparison. Im- 

 mei-se a fine needle in 100 ^f' Ale. to cleanse it; when dry again, prick the 

 finger with it, and bring a drop of blood upon a slide. Dilute with clear 

 saliva, free from bubbles, and cover. (The saliva is the best fluid for diluting 

 the blood. It keeps the form of the red corpuscles and is itself rich in leu- 

 cocytes.) Search for leucocytes. When found, examine for several minutes 

 300-600'' and observe the changes of form. These are rendered extremely 

 slow by the lowering of the temperature and soon stop, (cf . the difference be- 

 tween 98.6° F.. the temperatiire of the body and that of the microscopic 

 stage.) The movements are better seen by use of the '* warm stage," an ap- 

 paratus which heats the preparation by means of an alcohol lamp, or by using 

 the blood of some animal of lower normal temperature, as the frog. 



11. Heliozoa. 



These are radiate, free-swimming forms, found in clear water, captured 

 best by the towing net. They are thus difiicult to find and never at hand 

 when wanted. Bear them in mind, however, and be ready to recognize the 

 first one you meet in subsequent study of pond water. When one is found, 

 study and draw it. and if possible identify it by Leidy. 



