Ken YON, The Brain of the Bee. 149 



They all form a promiscuous group that might be, but for lack 

 of a better knowledge of them and their cells of origin, may as 

 well not be, subdivided. Almost all of them are known only 

 from fragments of which those shown in plates XXI and XXII 

 are the best examples. Some of them may possibly even be 

 fragments of motor-fibers. 



To these groups may be appended two others, one repre- 

 sented by the enormous fibers from the ocelli and the other by 

 the equally enormous fibers situated near the dorsal surface of 

 the ventral system and of the ventro-cerebron. They will be 

 considered in connection with the ocellar nerves. 



THE CONNECTIONS BETWEEN NERVE FIBERS. 



What facts I am able to bring forth bearing upon the 

 " contact " idea and the old " mesh-work " idea of the fibrillar 

 terminations, though more properly considered here, I will de- 

 fer until I have described the mushroom bodies, in connection 

 with which the facts mentioned occur. 



TRACHEA. 



Besides these neural elements and the sheaths surrounding 

 some of them, there are to be found large numbers of tracheal 

 fibers. In bichromate of silver preparations they are the first 

 elements to become impregnated and then are brought plainly 

 into view. The larger branches may be very readily recognized 

 in haematoxylin preparations. Their general tapering form and 

 the time of their taking up the bichromate of silver prevents 

 their becoming confounded with nerve fibers. 



To explain their origin it must first be noted that the brain 

 of the bee is surrounded by a number of tracheal sacs, the in- 

 ner walls of which closely cover it. Here and there tracheal 

 outgrowths from the sacs especially in the neighborhood of the 

 cell clusters pass into the brain. They branch more or less pro- 

 fusely among the cells and then send smaller branches into the 

 fibrillar substance as shown in fig. 29, PI. XXII, which repre- 

 sents a camera drawing of the tracheae of one of the mushroom 

 bodies. Tracheae almost identical in appearance with these, are 

 found on all sides of the brain. Others, however, of a larger 



