1898.] MICROSCOPICAL JOURNAL. 223 



brass : — Put two grains of lamp-black into any smooth, 

 shallow dish, add a little gold size and thoroughly mix 

 the two together. Just enough gold size should be used 

 to hold the lamp-black together. About three drops of 

 size, as may be had by dipping the point of a lead pencil 

 about half an inch into the gold size, will be right for the 

 above quantity of lamp-black. After the above are 

 thoroughly mixed and worked, add twenty-four drops of 

 turpentine and again mix and work. Apply thin with a 

 camel's hair brush, and when dry, a fine dead-black 

 will result. 



Practice.^ — It requires considerable experience to in- 

 terpret correctly the objects viewed in the field of a lens. 

 It is generally impossible for a person unaccustomed to 

 the instrument to know precisely what the field ex- 

 hibits. When experts bring their instruments into court 

 judges and jurors often take a look at an object and draw 

 the most erroneous conclusions. Air bubbles, oil bubbles, 

 stray debris and accidental particles are apt to most 

 strongly engross the attention. 



MuscA DOMESTiCA. — This is a common house-fly. On 

 account of the conformation of its mouth parts, this in- 

 sect cannot bite. Common and wide-spread as this 

 species is, there is very general ignorance as to its life 

 history and habits, except in its adult stage. Its length 

 of life in the adult condition is not certainly known. In 

 a warm climate it produces ten to thirteen generations 

 every summer. A single fly will lay an average of one 

 hundred and twenty eggs. Stables are their chief and 

 favorite breeding places. They are carriers of con- 

 tagion. In the autumn, they are attacked by minute red- 

 dish mites. As many as nineteen of these mites have 

 been found on a single fly. Soak the fly in a shallow 

 vessel in turpentine when the mites will crawl ofi" and 

 may be examined and mounted. 



