1. to condensers are few;Crossmon and Loewenstein;Matthaei; advises an " abbe " type to avoid any fluorescence from the cement between multiple lenses, which also absorb more light, and he specifies glycerol immersion of the condenser for maximum light transmission,1950
2. The objectives employed in fluorescence work are those in normal use. For the 4 mm. objective, one of N. A. 0.85 is preferable to;A, N.; Richards;Graham (1943) and Matthaei; Opinions differ concerning fluorite and apochromatic lenses,1943
3. 1951), but in general there is no need for any power higher than 4 mm;D. M. McCLURE has been mentioned (Kolmer, Spaulding; Robinson
4. The recommendations as to eyepieces differ widely. These fall into two groups: eyepieces of the powers in everyday use, and those of very much higher powers. Hagemann used a range from 3 x to 10 x, and Bogen;Lind (1949), and Popper and Szanto;et al. (1941), Lind and Shaughnessy; one of 5 x. At the other extreme, the use of eyepieces of 20 x is recorded by Richards,1941
5. has observed that binocular microscopes differ widely in their capacity to transmit light in the blue-violet range. This may be attributable to the reflecting prisms, as no comparable variations have been recorded between the objectives and eyepieces of different manufacturers. In any case, a monocular instrument is to be preferred;Matthaei,1950