22 WILLIAM PATTEN. 



In the younger specimens they are slightly expanded near the 

 top, and a flange-like rim is formed by the projection of the 

 cuticula into the outer end of the canal (fig. 23). 



The canals contain, besides the chitinous tubule, a varying 

 number of fibres, with here and there a few minute nuclei 

 (fig. 9, n. c). They can be traced a short distance only 

 toward the outer end of the canal ; in the opposite direction 

 they seem to run either over the outer surface of the olfactory- 

 bud, or apparently between its cells toward the interior. I 

 have never been able to trace them with certainty up to 

 nerve-fibres, although they appear to have such connections. 



The tubules isolated by maceration in Haller's fluid stain 

 deeply in methyl green and in acetic acid carmine, resembling 

 the chitinous tubules of the gustatory organs. They are 

 usually collapsed, and appear to be perfectly empty. Al- 

 though I have examined them in many ways, paying special 

 attention to their broken ends for protruding fibres, I have 

 never seen a trace of the axial fibres so conspicuous 

 in the other gustatory tubules. Isolated tubules from 

 the gustatory buds on the inner mandible sometimes show, 

 when treated with potash, a protoplasmic-like envelope with 

 spiral markings (fig. 14) ; others have two or more coarse 

 refractive fibres, often thrown into numerous irregular folds, 

 extending along their outer surfaces (fig. 16, a). The tubules 

 in the olfactory organ are very rarely convoluted, and they 

 never have the two refractive fibres just mentioned. When 

 the olfactory buds are isolated and examined whole, spindle- 

 shaped cells are often seen adhering to their outer surface, 

 also a few scattered nuclei that appear to belong to the 

 delicate membranous investment of each organ. 



The nerves that supply the olfactory buds are small 

 strands arising from an extensive anastomosing plexus found 

 everywhere beneath and around the olfactory buds. The 

 plexus itself arises from three large nerves, that I shall call 

 the lateral and the median olfactory nerves (PI. 2, fig. 18; 

 see also PI. 4, figs. 48 and 49) . 



