6 9 



3. Observe that one end of the ovum is always 

 stouter than the other. The stout end contains the 

 head of the embryo, and is the end from which the 

 young larva escapes. Note also that when Anopheline 

 eggs are seen at the side of vessels drawn up by capil- 

 larity the thick end is at the bottom. Examine the 

 surface of the water remaining in the hollow stopper or 

 receptacle, and observe that the ova of Anophelines are 

 laid singly without any cement substance, and float 

 singly or touching one another on the water. 



Fig. 24. Patterns formed by Eggs of Anopbelines 



4. Observe star-shaped patterns formed by some 

 species, or the arrangement in parallel groups assumed 

 by the ova of others (Fig. 24). Note that this arrange- 

 ment is dependent on physical causes (shape of the egg, 

 etc.), and not on the fact that the eggs are laid in such 

 positions. This is readily done by stirring up a number 

 of Anopheline ova on water, and noting how they tend 

 to form groups in triangles and star shapes (p. 186). 



5. Ascertain that Anopheline ova, when first laid, 

 are white, but rapidly darken and become black. 

 Observe that Anopheline ova are very often laid in 

 heaped-up masses, which eventually become dispersed 

 by waves, etc. Observe that the eggs then form 

 patterns. 



6. Place some half-dried mud in a flat dish, and 

 put this inside a piece of mosquito netting in which 



