OVARY AND OVARIAN EGG OF ANOPHELES 411 
caustic potash, i.e. the ‘ Biuret Reaction’, the granules tum 
a beautiful violet colour. 
Nitric acid turns the previously white yolk light yellow, and 
when excess of ammonium hydroxide is added the yolk turns 
a brilliant orange colour. (Xanthoproteic Reaction.) 
With osmie acid the granules turn yellow or yellow brown. 
These granules appear to be homogeneous and solid, as they 
can be broken by the pressure of a cover-slip. 
The other type of yolk consists of small granules 0-001 mm. 
in diameter, and these are found surrounding the granules of 
coarse yolk (fig. 11). They are chemically quite different from 
the large granules as they do not respond to any of the above 
reactions. They are certainly not fat globules, as might be 
expected, as they are not coloured in any way by osmic acid, 
either alone or in the presence of chromic acid in the form of 
Flemming without acetic: a test described by Gatenby (7). 
[ have not succeeded in making the fine yolk granules respond 
to any chemical reaction or stain in any way. In sections they 
appear as clear vacuoles, but they must be more than mere 
drops of watery fluid, as, if an egg is broken in water, they are 
seattered through the liquid as minute spheres which exhibit 
a very pronounced dancing movement. This movement comes 
to rest after a few hours, so that it is probably due to diffusion 
currents from the granules. 
It may be noted here that the fine yolk is a definite con- 
stituent of the mature mosquito egg, and is not an inter- 
mediate substance produced during the formation of yolk, 
as in the case of the ‘ granules adipeux’ of Pholeus phalan- 
gioides according to Van Bambeke (1). 
The protoplasmic portion is very inconspicuous in the 
mature mosquito egg. In sections it is seen as a network of 
fine threads, the meshes of which are occupied by the yolk 
eranules (fig. 11). At the periphery the protoplasmic threads 
are slightly thicker than in the remainder of the egg, and they 
form an ill-defined cortical layer. This layer is thickest at the 
two extremities of the egg, in each of whiclf it forms a small area 
of granular protoplasm free from yolk. Occasionally a few 
