326 N. E. McINDOO 



that has formed the hair. No hairs with sense cells were found 

 in any of these sections. 



In the front wing of a 19-day-old pupa the sense cells (fig. 

 19, SC) belonging to groups 1 and 2 occupy only about one- 

 half of the internal space. This leaves a large cavity, the blood 

 sinus {BlSin) for the blood, blood corpuscles {BlCor), and small 

 tracheal branch (Tra). Here as elsewhere the sense cells are sur- 

 rounded by a membrane, the neurilemma {Neu), which appears 

 as a single line. Often its nuclei {NeuNuc) are discernible. In 

 the front wing of the adult bee the sense cells (fig. 20) belonging 

 to groups 1 and 2 occupy nearly all of the internal space and 

 leave only a small cavity for the tracheal branch and blood. 

 In the hind wing of both the pupa and adult the space is rela- 

 tively larger. This indicates not that the sense cells of the adult 

 have increased in number, but in size. Since all the chitinous 

 structures are completely formed by the time the bee emerges 

 from its cell, the same number of pores would be expected in bees 

 just emerged as are found in adult ones. This was ascertained 

 to be the case, as was stated in discussing the disposition of the 

 pores in the worker. 



The nerve fibers of the sense cells run immediately into a 

 nerve branch (figs. 15 and 18, NB) where as individual fibers 

 they can not be traced farther. However, a longitudinal view 

 of a nerve shows that it is composed of many parallel fibers. In 

 the leg a branch of the nerve proceeds to each group of sense cells, 

 but single fibers (fig. 18, NF) run to the isolated sense cells. No 

 two of these branches are given off at the same time. A double- 

 walled membrane, the neurilemma (fig. 18, Neu) surrounds the 

 nerve {N) and its branches. The walls of the neurilemma con- 

 tain many small deeply-staining nuclei (NeuNuc). Inside these 

 walls among the nerve fibers there are many larger but less 

 deeply-staining nuclei (figs. 18, 20, and 21). A cross section of 

 the nerve shows a network of minute fibers, among which several 

 small dark nuclei (fig. 18, NeurNuc) stand out conspicuously. 

 These nuclei in both the nerve and its branches are probably 

 neuroglia nuclei. 



