126 LABORATORY WORK. 



tion through the base of a tentacle; is the tentacle hollow? 

 Can you trace both layers into the tentacle? Draw the 

 section. Trace the layers into a medusoid bud. Between 

 the layers in the bud are the reproductive products. 

 In a male specimen these will appear as a multitude of 

 dots (spermatozoa); in a female there will be a single egg 

 in each bud. In the egg make out the large mass (proto- 

 plasm) with near its centre a spherical mass (stained), 

 the nucleus. In the nucleus there will usually be seen a 

 deeply stained body, the nucleolus. Add a medusa-bud to 

 the last drawing. 



Read in this connection pages 154 to 156 upon the body 

 layers, and pages 140 to 142 upon the cell. Do the eggs 

 agree with the account of a cell? Examine both ecto- 

 derm and entoderm with the high power. Can you dis- 

 tinguish cells in either? Draw a bit of the wall greatly 

 enlarged showing the structure of both layers and bring- 

 ing out a thin structureless layer (the supporting layer, or 

 mesoglcea) between the two. 



