I 



CASTES OF TEEMOPSIS 505 



rounded surfaces seen in the mushroom bodies of all the other castes 

 (fig. 4, b,c,d) are slightly convoluted in the first form, the outer 

 lobe together with part of the inner, curving upward to a level 

 above the inner lobe. Sections show that the three cell groups of 

 the mushroom bodies described in the brain of Reticulitermes, 

 Thompson ('16), are also present in Termopsis, and that similarly 

 all the cells are small and of equal size. The relations of the 

 anterior and posterior roots of the mushroom bodies are also the 

 same as in ReticuUtermes and the other termites studied by the 

 writer. The protocerebral lobes are connected by a broad ven- 

 tral, and two slender dorsal commissures. The central body is 

 largest in individuals of the first form. A frontanel nerve is 

 present in Termopsis, homologous with the frontanel nerve de- 

 scribed in ReticuUtermes, Thompson ('16), running from the 

 basement membrane of the frontal gland down to the upper sur- 

 face of the ventral protocerebral commissure, in the same sec- 

 tions with the posterior roots of the mushroom bodies. There is 

 nothing essentially pecuHar in the other parts of the brain. 



The brain in the younger first-form nymphs (fig. 1, b) differs 

 from that of the mature nymphs (fig. 1, a) in the smaller optic 

 lobes and the smooth rounded contour of the mushroom bodies. 

 In this caste these characters are due to the age of the individuals, 

 but the same characters occur as castal differences, as will be seen 

 in the description of the brains of the other castes and in figure 4. 



The frontal gland. The 'frontal gland' of Termopsis is of the 

 type termed by Holmgren a non-glandular Tontanel-platte.' 

 It consists, in the first form nymph (fig. 5, fg) of a broad but shal- 

 low depression of modified hypodermal cells covered above by 

 their own cuticle and resting upon a base of connective tissue 

 which tapers to a point, and from which the frontanel nerve 

 (Thompson, '16) takes its way downward and inward between 

 the mushroom bodies to the protocerebral tissue. The hypoder- 

 mal cells (fig. 5, hy) of the head of Termopsis are tall and slender 

 epithelial cells, the supporting cells distinctly columnar in form 

 and interspersed with occasional gland cells, but on the frontal 

 surface within the area of the frontal gland the height of the 

 supporting epitheHal cells is very greatly increased, and similarly 



