PRACTICAL DIRECTIONS 259 



PRACTICAL DIRECTIONS. 



HsBmatoCOCCUS- Examine a drop of water containing Hsemato- 

 coccus, first with the low power, and then, after putting on a cover- 

 glass, with high power. Note — 



1. Their roanded/orm and green (or red) colour ; the thick cellulose 

 cell-wall ; the protoplasm enclosing (a) chromatophores , containing 

 chlorophyll (ttit red colour is due to another colouring matter, hamato- 

 chrome), and (b) a central nucleus, seen better later ; and in the active 

 forms, the two flagella. Sketch. 



2. Dissolve out the chlorophyll by adding alcohol ; the nucleus will 

 then be visible, and may be made more distinct by staining with 

 methyl-green, magenta, or iodine. After treatment with iodine, a 

 bluish colouration will be seen around the small starch-containing 

 pyrenoids. 



3. Treat some specimens either with strong iodine solution and then 

 with sulphuric acid (75 per cent.), or with Schulze's solution, which is 

 prepared as follows ; — Make about 25 cc. of a syrupy solution of zinc 

 chloride, and let it stand for a short time ; then pour off the clear fluid, 

 saturate it with potassium iodide and add iodine until the solution has 

 about the colour of sherry. Note the colouration of the cell-wall. 



4. In the living specimens note also the mode of division into 

 4 megazooids or into 16 or 32 microzooids, and observe their move- 

 ments when set free. Sketch. 



Euglena. Examine a drop of water containing Euglena with the 

 low power, then cover, and put on the high power. Note — 



1. The spindle-shaped form of the body, and its changes of form in 

 contraction and expansion. 



2. The Xoagflagellum. 



3. The superficial cuticle, and the mouth and conical depression 

 {gullet) at the anterior end. 



4. The central part of the body, which contains chlorophyll, except 

 at the two ends. Near the middle is a nucleus enclosing a nucleolus, 

 and near the anterior end a non-contractile space into which a contrac- 

 tile vacuole opens, close to which a red pigment-spot is situated ; the 

 colour of this is due to haematochrome. Grains of paramylum may be 

 recognised near the centre of the_ body. Sketch before and after 

 staining as above, 



S 2 



