T. C. WHITE ON INSECT DISSECTION. 35 



requires and brought to bear on the subject. The lower power 

 microscopical objectives, such as the 1 inch, 1| inch, and 2 inch, may 

 also be used, being supported in such an arrangement as that first 

 described, but far better results will be attained by the use of an 

 erecting glass in the tube of your microscope, because that affords a 

 ready method of varying your magnifying power and adapting it 

 to the dimensions of the work under dissection, and rendering what 

 would be otherwise very difficult a simple matter of steadiness of the 

 hand. 



Our next consideration must be in the direction of a good light, 

 and this, with some dissectors, is so important that it occupies a 

 priority over magnifying powers ; but, however much we may differ 

 from them in this point, there cannot be a doubt about this opera- 

 ting as a most important factor if we would get good results ; and 

 although a successful dissection may be made with a full light con- 

 densed on your work, yet better will be obtained by your light being 

 supplemented by the magnifying power. The plan 1 have adopted 

 for this is inexpensive and simple — a Florence oil flask is well 

 cleansed and filled with water, then securely corked and waxed to 

 prevent leakage. It is then supported longitudinally by a tube which 

 grasps its neck, the tube itself being supported on an arm held on a 

 heavy foot ; this gives the power of adjusting the focus of its rays 

 upon your dissection to any extent you may deem desirable, while 

 should a fracture of your flask occur it is easily and cheaply replaced. 



The morning light is better than any other, the horizontal rays 

 falling more agreeably on your work than the vertical rays from a lamp 

 at night, and in the morning the hand is steadier for the work. An 

 advantage is gained sometimes in dissecting by transmitted light, 

 especially if you can impart a blue tone to it ; at other times greater 

 advantage is attained by dissecting by reflected light, and on a black 

 ground. As an aid, I would also recommend that your subject should 

 be stained by carmine or logwood before dissecting. 



The instruments necessary for insect dissection are not expensive, 

 and may nearly all be prepared at home ; but one essentially useful 

 is a pair of small spring scissors. These cannot be dispensed with, 

 nor can a firm but fine pair of forceps, for before you can reach the 

 internal organs of an insect it is necessary to remove the external 

 chitinous integument, and in some cases this is so hard that in the 

 case of the stag beetle a pair of wire nippers will not be too strong 

 for this purpose. The cutting instruments, the scalpels, in fact, 



