ORIGIN OF CASTES OF TERMITES 109 



and differentiation of the two brains and their parts in the newly 

 hatched nymphs. 



The mushroom bodies of the reproductive type project prom- 

 inently from the future dorsal^ surface of the brain, and their 

 surfaces are grooved, so that the outer and inner lobes are 

 already indicated, and the pointed outer lobes are especially 

 prominent. The mushroom bodies of the worker-soldier type 

 are smaller and much less differentiated at this age. The outer 



m b 



o I 



Fig. 2 Superimposed outlines of the brains of the two types of L. flavipes, 

 the reproductive type in heavy outline, the worker-soldier t3'pe in broken line. 

 A, brains of the newly hatched nymphs, body length 1.1 mm. ; b, brains of njTnphs 

 with eleven antennary segments, body length 1.4 mm.; c, brains of njTnphs with 

 twelve antennary segments, body length 2 mm.; m.b. mushroom bodies; o.l. 

 optic lobes; a.l. antennary lobes. Oc. 6, obj. 16, table level, reduced one half. 



surface is smooth, since the inner and outer lobes are not yet 

 indicated. The optic lobes of the reproductive type are very 

 large and project laterally and downward toward the antennae. 

 The outline of the downward curve of the optic lobes of this 

 type is the best means I know for distinguishing the two kinds 

 of brains, (figs. 41, 42), In the worker-soldier type the optic 

 lobes are small and do not point downward. The antennary 

 lobes are far greater in bulk in the reproductive than in the 

 worker-soldier type. The relative size of these three parts 

 of the brain is even more apparent in sections than in whole 

 mounts. 



^ In life the heads of these termite nymphs are held in a slightly slanting 

 position, making a large obtuse angle with the long axis of the body, so that the 

 morphological dorsal surface becomes frontal or anterior. In the whole mounts 

 the heads are flattened out and the frontal surface becomes dorsal again. The 

 same terms of direction, however, will be used as for the adult termites. In 

 describing the heads the terms anterior and posterior imply toward and away 

 from the frontal surface, in like manner dorsal and ventral imply toward or away 

 from the vertex of the head. 



