476 F. P. SMITH ON SPIDER DISSECTIONS AS MICROSCOPICAL OBJECTS 



The removal of the clip is something of a problem. In almost 

 every case a bubble of air will rush in unless a special pre- 

 caution is taken to avoid it. This is exceedingly simple to 

 accomplish — so simple, in fact, that it escaped my attention for 

 a considerable time and lured me into many fruitless experiments 

 with far more elaborate methods. The clip is simply removed 

 under water and the slide allowed to remain submerged for a 

 few minutes. A small quantity of water will enter, but this will 

 not in the least impair the mounting medium. The clip is 

 then wiped as far as possible, allowed to dry thoroughly, a ring 

 of gold-size is added and, a couple of days afterwards, a ring 

 of Club black. The object can be examined at once with dark- 

 ground illumination, but generally improves after a few days 

 when the glycerine has thoroughly penetrated it. 



Probably some one will point out the advisability of doctoring 

 the gold-size with white lead, red lead, litharge, or some other 

 metallic salt, or will dilate upon the advantages of putting 

 on seven rings of gold-size and seven rings of Club black 

 alternately at intervals of fifteen days. Probably there is wisdom 

 in these suggestions ; but the method here advocated has at least 

 the advantage of simplicity, besides being expeditious, matters 

 of great importance to a man who needs to prepare large series 

 of slides for research work. I might mention that I have a 

 considerable number of such preparations dating back for more 

 than two years, and that in no single instance has an air-bubble 

 penetrated in spite of a good deal of very rough usage. Experts 

 wag their heads wisely and tell me they cannot last must longer ; 

 but even if this is so I consider they have already more than 

 repaid the trouble taken to prepare them. 



Talking of air-bubbles, some one will assuredly remark that 

 it is a good plan to " put a bubble in the mount " as a safety-valve 

 for heat expansion. This may be so. Personally I detest a 

 bubble in a mount, especially in the case of a spider palpus, for 

 sooner or later a fragment of its spherical nothingness is almost 

 sure to become entangled with the complex structures of the 

 object and interfere with critical examination. The theory 

 of the safety-valve is, however, worth bearing in mind, if only 

 as an excuse for the presence in a cell of a refractory bubble 

 which defied the mounter in his efforts to exterminate it. 



J own. Quckett Microscopical Club, Ser. 2, Vol. 2l., No. 65, November 100!). 



