ZOOLOGY AND BOTANY, MICEOSOOPY, ETC. 



917 



If the apparatus is adjusted in the manner described it will work 

 equally well from the beginning to the end. It cannot be used for 

 friable sections ; in such cases a section-stretcher is not applicable. 

 The block of paraffin to be cut is to be so shaped that it presents the 

 section shown in the figure. Some paraffin is left on the side towards 



Fig. 172. 



^y 



3 



the edge of the knife, so that before it reaches the object it may find 

 something to cut, and the opposite side is pared away so that the 

 section (as is shown in the figure by the dotted edge of the knife) 

 may adhere only by the posterior corner and not along the whole 

 margin of the edge of the knife, and can therefore be easily removed 

 by a pincette. 



Cutting- Sections of Probosces of Honey-feeding Insects.* — 

 F. Cheshire recommends that the insect to be operated upon should 

 be kept fasting for some time and then fed upon honey mixed with 

 gelatine impregnated with some highly coloured dye. The insect 

 should be immediately decapitated and the head rapidly cooled, and 

 then imbedded in gelatine and the section cut by the microtome. 

 The mouth passage is then easily seen from the presence of the dye. 



By the use of this method Mr. Cheshire was easily able to make 

 out the structure of the extreme apex (" Eeaumur's bouton ") of the 

 tongue of the honey-bee, about which so much difference of opinion 

 has existed. He has also found that the tongue is neither a tube 

 through its entire length nor a gutter or trough, but is in reality a 

 trough on the upper side at the apex, and a tube for the rest of its 

 length. 



* Proc. Eatamol. Soc. Loud., 1883, p. xix. 



