238 THE MICROSCOPE. [December, 



rod of the stand and place the card in the two little bends at ^, 

 and the lamp is ready for use. An ordinary side condenser can 

 be substituted for the ground glass, and a cheap tin reflector for 

 the card. I use the lamp in this way for photo-micrography and 

 find it excellent. If a blue glass is desired, thoroughly clean a 

 spoiled 4x5 dry plate or other piece of clear glass the same size, 

 and flow with " King's transparent blue lacquer;" don't apply 

 the lacquer with a brush, as it leaves unsightly ridges. Nearly all 

 retort stands have light bases ; therefore remember that when the 

 " centre of gravity falls outside the base" you are very likely to 

 '^ hear something drop." 



By the way, a J-inch thin glass circle, if coated with the blue 

 lacquer and stuck on the lower end of the cylinder holding the 

 diaphragms (in a continental stand) with a little parafiin, makes 

 a good '' moderator" for night work. 



Tlie Brine Shrimp of the Great Salt Lake. 



By J. E. TALMAGE, Ph. D., F. R. M. S., 



SALT LAKE CITY, UTAH. 



The brine shrimp, Arteniia fertilis (Verril), is a tiny crus- 

 tacean abounding in the water of the Great Salt Lake. They fre- 

 quent the surface ; indeed I have never taken a specimen from a 

 depth beyond two feet. They may be found in the lake at all 

 seasons, though they are most numerous between May and Octo- 

 ber. I have taken them in the midst of winter, when the temper- 

 ature of the water was far below the freezing point ; it will be 

 remembered that the concentrated brine of the lake never freezes. 

 The females greatly preponderate ; in fact, during the colder 

 months it is almost impossible to find a male. In the latter part 

 of summer the females are laden with eggs, from four to sixteen 

 having been repeatedly counted in the ^^^ pouch. The males 

 are readily recognized by the very large claspers upon the head. 



The artemiae frequent the shores during calm weather, but 

 rain drives them into the lake. Oftentimes they congregate in 

 such numbers as to tint the water over wide areas. They are 

 capable of adapting themselves to great variation in the composi- 

 tion of the water, as must necessarily be the case with any inhab- 

 itant of the Salt Lake, for that body of water is subject to wide 

 fluctuations in bulk and composition. Aside from the long 

 periods of rising and falling of the waters, there are great annual 

 variations caused by the relative supply of water through rain and 

 snow-fall and the loss by evaporation. Beside the annual fluctu- 

 ation, the lake is at present steadily falling, and the waters are 

 consequently growing more concentrated. I have specimens of 



