Ken YON, The Brain of the Bee. 141 



enter. In such cases the part most exposed would be incrust- 

 ed, while that opposite would be entirely free. Other methods 

 were thought of and tried. That of wrapping a brain in filter 

 paper was considered too rough a treatment ; covering a brain 

 with celloidin failed. Had the one suggested by Retzius (92 h), 

 namely, of dipping a brain in warm gelatine, been thought of or 

 known in time, it would doubtless have given excellent results. 



The nitrate of silver was employed in strengths ranging 

 from y2% to 2%. The stronger solutions, though giving 

 stronger impregnations, less evidence of beading, or fuller fibers, 

 have the disadvantage of being more inclined than the weaker 

 solutions to form artifacts. A solution of i % strength was 

 finally adopted for leaving the specimens in over night or until 

 I was ready to section them. 



Generally only one or two immersions in the fluids was 

 given the specimens, since it was desirable to have only a few 

 fibers impregnated so that very thick sections could be cut and 

 thus give the entire trajectory or as much as possible of a fiber 

 unobscured by other details. 



The impregnated brains were transferred to absolute alco- 

 hol and then to celloidin. Where they were entirely free from 

 the head or from chitinous particles that would tend to prevent 

 them from becoming fairly saturated or surrounded with the 

 celloidin, sections wese cut within two hours from the removal 

 from the silver solution. But where they were surrounded by 

 the chitinous cephalic capsule from six to twenty-four hours 

 were found necessary to form a celloidin block of a consistency 

 sufficient to prevent tearing and breaking of the sections. 



Sections were cut all the way from twenty to two hundred 

 and ten microns thick, thus, in the thickest, making only three 

 or four frontal sections to a brain. 



General Description. 



External appearance. 

 Under the general term "brain" I here understand the 

 whole of the neural mass included within the head, excepting 

 only the two small ganglia generally known as the stomatogastric 



