BRAIN OF THE 'WHITE ANT' 577 



opening may be observed in the cuticula above the anterior end 

 of the gland, but I have not been able to distinguish any such 

 opening in the worker or in the two nymphs. The opening is 

 situated in a shallow depression of the surface, the fontanel, 

 which is paler than the surrounding skin. 



The frontal gland differs greatly in size in the various castes. 

 It is smallest of all in the worker (fig. 11) and greatly elongated 

 in the soldier (fig. 12). In neither of these castes does the 

 frontal gland completely fill the space between the mushroom 

 bodies. In the sexual forms the true adult (fig. 9) has the largest 

 frontal gland; the nymph with long wing pads (fig. 8) has a 

 gland of similar proportions but smaller; the njmphs with short 

 wing pads (fig. 10) has an even smaller gland. In all the sexual 

 forms the frontal gland completely fills the space between the 

 mushroom bodies. 



Looking down into the frontal gland as it is seen in surface 

 views is like looking into a shallow crater. The edges rise into 

 folds which approach each other and nearly meet at the antero- 

 ventral end and enclose the central lumen. Sections show that 

 the marginal cells of the gland are directly continuous with the 

 hypodernuil cells and that the cuticula above the center of the 

 gland is slightly depressed and thin, consisting only of the pri- 

 mary or outer cuticula, the secondary, inner, cuticula ending 

 at the gland margin. Tliis depression and thinning of the cutic- 

 ula is the structural explanation of the pale 'fontanel' spot seen 

 on the outer surface of the head. 



In the series of sections seen in figures 13 to 20, the first indi- 

 cation of the frontal gland is seen in a group of elongated hjiDO- 

 dermal cells (fig. 13,f.g.) lying in the median line directly beneath 

 the cuticula, wliich is here of normal thickness. This group of 

 cells forms the anterior margin of the frontal gland and it should 

 be noted that it occurs in the same frontal section as the simple 

 eyes, or ocelli, oc, a point wliich will be further discussed later. 

 Figure 14, which is six sections farther back in the series, includes 

 a section of the anterior part of the frontal gland, f.g. The 

 high columnar cells of the gland are continuous with the low 

 cuboid hjTDodermal cells; the cuticula is slightly depressed and 



