10 LABORATORY DIRECTIONS IN 



this sketch, the chloroplasts may be added to the figure of the cell wall 

 already drawn. In this case plastids shaped like two biscuits fastened 

 together should be included if they are found. Be on the lookout for 

 plastids in other unstained cells to be studied later. 



2c. In mounted sections of Hydra study the cells of the innermost 

 layer. Hydra is a small many-celled animal, having certain affinities 

 with jellyfishes, corals, sea-anemones and hydroids. Its body is com- 

 posed of two distinct layers of cells separated by a non-cellular layer. 

 Note particularly the large clear spaces within the inner cells. These 

 spaces are vacuoles. Draw in detail a group of three cells of this layer 

 showing structures present. 



2d. Examine specimens of Phacus or Euglena (both green flagellate 

 Protozoa) for paramylum bodies. These are granules of stored food, 

 resembling starch in its chemical composition. They are colorless. 

 Their shape differs in various species, being discoid in some, ring-shaped, 

 rod-shaped, or polyhedral in others. If Euglena is used for this study 

 flatten the specimen by withdrawing water from the preparation and look 

 for minute colorless bodies among the green. Do not mistake the 

 rounded nucleus near the middle of the body and the reservoir of the 

 contractile vacuoles near the anterior end for the paramylum bodies. 



2e. Remove a frog's egg from its jelly-like covering, then tease out 

 (tear up finely with needles in water) the substance of the egg upon a slide, 

 separating the particles until they form a very thin layer on the slide, 

 and mount under a cover-glass. Examine with the microscope. The 

 fine granules are yolk material (stored food). Sketch a group of them. 



3. What are Some of the Structures of the Nucleus? 



3a. In longitudinal sections of a dorsal root ganglion (a small mass 

 of nervous tissue occurring near the junction of spinal nerves with the 

 spinal cord) of a cat look for a single rounded body near the center of 

 many of the nuclei. This is the nudeolus. Note its color. Observe 

 the chromatin which occurs as granules in the nucleus. Compare the 

 colors of these granules. Sketch in detail a cell of the ganglion to show 

 nucleolus or nucleoli and chromatin granules. The sections on these 

 slides were stained with two stains. All parts of each cell were sub- 

 jected to the same processes. On what basis may the difference in color 

 between the nucleolus and the chromatin granules lie explained? 



4. What is the Structure of a Simple Living Cell? 

 Amoeba furnishes an example of such a cell. 



4a. Mount some ooze from a culture containing Amu l>a. The 

 student should endeavor to find a specimen for himself. If an amoeba 

 cannot be found ask help, but do not discard the slide. It may have 

 amcebas on it, even if the student has not been successful in identifying 

 one. 



