260 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Some satisfactory slides have been made from heads which re- 

 mained in celloidin for three months. Instead of transferring 

 the specimens to thicker solutions, it is easier and just as well 

 to let the 4-per-cent. solution gradually thicken by evaporation. 

 When the celloidin has reached a jelly-like consistency, the 

 heads were removed and hardened in chloroform. On entering 

 the chloroform the celloidin will usually turn opaque, but this 

 condition disappears as the hardening process is completed. 

 When the specimens are hardened, usually from one to several 

 hours, they may be placed in the paraffin bath, and in another 

 hour they are ready to be molded into blocks of paraffin. 

 The specimens may now be kept indefinitely. 



The above method is entirely satisfactory, but it is long and 

 cumbrous. The Gilson process described by Lee is much more 

 expeditious. The object is dehydrated, soaked in ether, and 

 put in a test-tube with a thin solution of celloidin. The tube 

 is then dipped into the paraffin bath and the solution boiled 

 down to about one-third of its volume. The mass is then turned 

 out and hardened for several hours in a mixture of equal parts 

 of chloroform and cedar-wood oil. The specimens may now be 

 molded into blocks of paraffin as before. The best results are- 

 obtained by dry cutting. 



For staining, Delafield^s hsematoxylin and picric acid have 

 been found most useful. The hsematoxylin is a good nuclear 

 stain, while the picric acid is a valuable secondary stain for dis- 

 tinguishing chitin. In staining, the usual method of procedure 

 is followed. The sections may be cleared in cedar-wood oil or 

 other clearer and mounted in balsam. 



NOMENCLATURE. 



The nomenclature of the insect head has been based on ana- 

 tomical work entirely, and for that reason it has little morpho- 

 logical value. Some of the primitive sclerites are indistinct, 

 while others have developed greatly. The result is that a given 

 named area may include several sclerites or perhaps only a 

 portion of one. This nomenclature, however, is sufficient for 

 the .description of parts, and when supplemented with explana- 

 tions it will serve for morphological work; All terms denoting 

 location of parts are used with the head in the feeding position. 

  The beak is then at right angles to the body line. 



