ORIGIN OF CASTES OF TERMITES 111 



two slender mm. retractor fontanellae, shown in figure, 35 f.g., 

 attached to the mesenchymatous sheath, just beneath the hypo- 

 dermis in the frontal region. The empty basement membrane 

 may be observed above the brain in subsequent sections. 



It will be recalled that the tentorium, or the chitinous frame- 

 work within the head, originates as a cuticular excretion from 

 the surface of a number of hypodermal invaginations that later 

 meet and fuse. The tentorial invaginations still retain their 

 connections with the hypodermis in this and in several succeed- 

 ing phases, but very little of the chitinous cuticula is yet formed. 

 The great delicacy of all parts of the head except the brain, is 

 one of the causes of the frequent shrinkage observed in the heads 

 of fixed specimens of the early phases. So far I have been unable 

 to distinguish the lateral ocelli in the newly hatched nymphs. 



The compound eyes are small and apparently equal in size 

 in the two types of the newly hatched nymphs as seen in the 

 whole mounts from which figures 6 and 7 are drawn. But in 

 sections of this phase, (figs. 18, 19, 41, 42,) it may be seen that, 

 from the beginning, there are differences between the two kinds 

 of eyes. The compound eyes of the worker-soldier type of 

 newly hatched nymph (figs. 19, 42) are very simple in structure, 

 consisting merely of two ill defined layers of scattered undiffer- 

 entiated cells. In one newly hatched worker-soldier individual, 

 not figured, the eyes were composed of only a single row of cells. 

 In the compound eye of the reproductive type (figs. 18, 41) 

 the cells are in two layers, and a few are differentiated into large 

 and small cells which already show a tendency toward the future 

 grouping. This eye is almost twice as thick as that of the worker- 

 soldier and contains a few more cells, but the two sections have 

 about the same length, indicating that the diameter is nearlj'- 

 similar in both types of eyes. The fibers of the optic nerve 

 may be observed issuing from the inner surface of the eye of the 

 reproductive type, figure 18. These were not observed in the 

 worker-soldier eye of this age, although present in older phases. 



V. Rosen ('13), in a study of the termite eye, states that in 

 L. lucifugus the compound eye 'Anlagen' are similar in all 'in- 

 different larvae,' and in the youngest 'small headed' and 'large 



