71 



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 capillarity 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. 



<m> 



Fig. ig. Patterns formed by Eggs of Anophelines 



4. Observe star-shaped patterns formed by 

 some species, or the arrangement in parallel 

 groups assumed by the ova of others (Fig. ig). 

 Note that this arrangement 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 {Vide p. 221). 



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. 



