548 CAROLINE BURLING THOMPSON 



bei den 3 Formen eine verschiedene Grosse. Bei der Arbeiterin 

 ist er verhaltnissmassig sehr gross entwickelt, beim Mannchen am 

 kleinsten, wahrend das Weibchen ungefahr in der Mitte zwischen 

 beiden steht. Eine Vergleichung der Tafelfiguren 21 bis 33 (L.a.) 

 fiihrt uns dies schon ausserlich vor Augen." Pietschker's text 

 figure 14 also shows that the fibrous core of the worker is larger 

 than that of the queen. 



The origin and distribution of the antennary nerves has been 

 studied only in the queen of Camponotus, but my observations 

 in this form are entirely in accord with those of Janet ('05), in 

 the brain of Lasius niger. The five pairs of antennary nerves 

 of the Camponotus queen leave the antennary lobes in two bundles, 

 the first anterior, and arising from the outer, lateral surface, the 

 second posterior, and arising from the inner or median surface. 

 From the anterior bundle arise three nerve trunks, two large and 

 one small, and a second small nerve arises from one of the large 

 trunks. From the posterior bundle a single trunk originates, 

 dividing almost immediately into four branches. These nerves 

 correspond to the five pairs of nerves described by Janet, and 

 are named as follows: from the anterior bundle (1), (2), two large 

 nerves which are the ''antennary sensory nerves I and II" of 

 Janet; (3) the small nerve trunk is the antennary motor nerve 

 to the segments of the antenna, the ''funicular nerve" of Janet; 

 (4) the second small nerve arising from one of the larger trunks 

 is the "sensory chordotonal nerve" of Janet; (5) the nerve from 

 the posterior bundle, which divides into four branches, is the 

 "motor nerve" of Janet, supplying the four muscles of the basal 

 segment or scape of the antenna. 



11, THE TRITOCEREBRAL LOBES, AND THE TRITOCEREBRAL NERVE 



The tritocerebrum, or the region corresponding to the third 

 head segment, is very much reduced in the ant. The tritocere- 

 bral nerve (fig. 16, tr.n.), which is median and unpaired and lies 

 beneath the esophagus supplying the inferior dilator muscle of 

 the pharynx, has paired roots which arise from two very small 



