ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 113 



creatures are of getting to the edge of the drop of water in which they 

 are placed, and to shift them to the centre is frequently a very tedious 

 work, and is often fatal to the animal." 



To remedy this defect, Mr. Rousselet " had a life-box constructed in 

 which the glass tablet is somewhat reduced in diameter, but the outer 

 ring is enlarged sufficiently to allow any high power to focus to the very 

 edge of the glass tablet, and the result is very satisfactory. An object 

 lying anywhere in the life-box can be reached by the condenser from 

 below, and by both low and high powers from above ; besides which, it 

 acts as a very good compressor, capable of fixing, without hurting, the 

 smallest rotifers, and, when you know how to do it, it is also possible to 

 get a rotifer in so small a drop of water that it is unable to swim out of 

 the field of view of a 1/4 in. objective." He has had it in constant use 

 for animals of all sizes, from the smallest infusoria to tadpoles. 



Mr. Rousselet has also had a small screw compresser, made on the 

 same principle ; " it is very simple and effective, and allows of regulating 

 the pressure to a nicety." 



Large form of Abbe Camera Lucida.* — Dr. Zeiss makes a form of 

 this camera lucida with a larger mirror and a longer arm than the one 

 first issued. j The larger form (only made to order) is recommended by 

 Dr. P. Mayer. The advantage of it he considers to be that it enables 

 the whole field of vision to be utilized without any perceptible distortion 

 of the image, and it is thus especially useful in drawing comparatively 

 large objects with low powers. With the smaller camera the whole field 

 can be projected on the drawing-paper only by giving the mirror an 

 inclination differing so much from the angle (45°) required for accurate 

 drawing that the image is more or less disproportioned. Dr. Mayer 

 further says that " the Abbe camera is superior to that of Oberbiiuser in 

 two important particulars : it gives a much larger field of vision and 

 better light. Its construction does not admit of use with the Microscope- 

 tube in a horizontal position. This is a defect which ought to be at 

 once corrected. The Abbe cameras, especially the larger one, can bo 

 used to great advantage with the embryograph of His. It is only 

 necessary to add to the stand a horizontal arm, to which the camera can 

 be fastened." 



May's Apparatus for Marking Objects.^ — Mr. R. Hitchcock, in 

 reference to Schiefferdecker's apparatus,! calls to mind a " much simpler, 

 but no doubt quite as efficient device for the same purpose," that he has 

 used for years, made by Mr. May, of Philadelphia. It consists of a 

 simple rod of brass about 1/4 in. in diameter, with a screw at the top 

 that fits into the nose-piece in place of an objective. A tube fits loosely 

 over this rod, bearing a diamond point below, slightly eccentric. This 

 is turned by a milled collar, so as to scratch minute circles on the cover- 

 glass. 



Simple Method of Warming and Cooling under the Microscope. || — 

 Heir H. Dewitz describes a very simple apparatus for warming and 

 cooling objects under the Microscope. It only cost 2s., and for many 

 purposes proved entirely satisfactory. 



Take a round leaden box, 0'08 m. in diameter, 0-03 m. in height at 



* Amer. Natural., xxi. (1887) po. 1040-3 (1 fig.). 



f Cf. this Journal, 1883, p. 278.' 



X Amer. Mon. Micr. Journ., viii. (1887) p. 207. $ See this Journal, 1887, p. 468. 



|| Arch. f. Mikr. Anat., xxx. (1887) pp. 666-S (1 fig.). 



1888. i 



