50 THE AMERICAN MONTHLY [Feb. 



terior where it then thins out into a semi-transparent, 

 muscular or contractile tissue, to its connection with the 

 opposite side of the ovipositor, thus forming a tube 

 througli which the eggs are extruded. 



Along each side of the middle piece extends a "t" 

 shaped rail, better shown in figure 5, r ; this figure being 

 the same as 4 with the parts separated. 



While the insect is engaged in the act of sawing, the 

 ovipositors slide backward and forward on these T shaped 

 rails, being held in place and guided by the central piece 

 or so-called sheath, which as shown in section is trussed 

 in such a manner, that it might serve as a model of rigid- 

 ity combined with lightness and strength. 



But the most unique feature of this beautiful piece of 

 mechanism is shown in the pair of hooks seen in the upper 

 part of figure 4, or more distinctly in figure b,h, k, where 

 they are separated. (This drawing is the same as part 

 of figure 4 but in separating the parts on the slide they 

 were turned over and thus reversed). 



In viewing these sections there is seen an outer branch 

 h, figure 5, resembling a thumb which closes over the op- 

 posing hook thus enabling it to maintain a firm hold. 



These hooks, as seen in section, are of course folds 

 along the whole length of the ovipositors which enable 

 the insect to hold these two margins together, or at will 

 to separate them, as it must necessarily do in cutting the 

 two diverging grooves. 



The figures here given were traced under the camera 

 lucida, and shaded from their appearance under the mi- 

 croscope. 



Should any amateur microscopist desire to test his 

 skill at section-cutting, I would recommend him to try 

 the mouth parts of a dry Cicada, and make a section that 

 will leave all the parts in their natural position. 



From what I observed during the visit of the 1894 brood 



