ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 907 



homoeopathic chemists, about 1 in. long and l-ith in. wide at the 

 mouth. This is inserted into a hole cut in a wooden slide, and its rim 

 prevents its falling through. Another wooden slide has a hole cut 

 through it of rather larger diameter, and on the top side a thin glass 

 cover is fastened with shellac glue. This slide is laid on the other. 

 The glass cover forms a lid, which closes the tube bottle, and is held 

 in its place by an elastic indiarubber band. A little cotton wool is 

 put into the bottom of the tube to shorten the space, to suit the 

 length of the fly, which must be inserted mouth uppermost, and kept 

 moderately near the glass cover, upon which a drop of syrup is placed. 

 Flies will readily feed in this position, and they are sufBiciently limited 

 in the power of lateral motion to be easily kept in view with 1^ in. 

 or 1 in. objective. 



Wenham's Reflex Illuminator.* — Mr. Wenham devised this 

 apparatus for the illumination of balsaraed objects, and also pointed 

 out that, with dry-mounted objects on the cover-glass, specimens are 

 frequently met with which have dropj)ed on the surface of the slide 

 itself, and may be seen "self-luminous" with the reflex illuminator 

 as with the immersion paraboloid ; but the direction of the light is 

 limited to one azimuth, which may be varied by rotating the illu- 

 minator. Mr. J. Swift " cannot, however, express a favourable opinion 

 of either of these methods of illumination, on the ground (1) that 

 objects such as diatoms, mounted in balsam, are too transparent to be 

 viewed by light reflected from their surface only ; and (2) the viewing 

 objects as ' self-luminous ' by means of light deflected or scattered 

 within their substance has not led to any useful result, though the 

 method has been known to microscopists since Mr. Wenham's publi- 

 cation of it in 1856. It appears to the author that the reflex illu- 

 minator may be used effectively to illuminate balsamed objects by 

 transmitted light of great obliquity — i. e. of obliquity within the 

 balsam, which can only be obtained by immersion or equivalent 

 means; it is then as an oblique illuminator iov transmitted light that 

 he would recommend its use. This action of the apparatus can be 

 utilized only in conjunction with an immersion objective whose aper- 

 ture exceeds 82^^ measured in crown glass." 



It should be noted that this action of the reflex illuminator was 

 first utilized by Mr. Samuel Wells, of Boston, U.S.A. So far as our 

 experience goes, the use of the reflex illuminator as an oblique 

 transmitter is a very cumbersome method compared with the admirable 

 simplicity of the oil-immersion condenser, or as compared with the 

 simple hemispherical lens placed in immersion contact with the base 

 of the slide. 



Practical Benefits conferred by the Microscope. — Prof. E. Eay 

 Lankester in his Presidential Address to the Section of Biology at the 

 Southport meeting of the British Association for the Advancement of 

 Science, strongly advocated the endowment of research, especially in 

 Biology. Keferring to the Microscope he said, " I need hardly remind 



* ' The Microscope and Accessory Apparatus,' 1883, pp. 50-2 (1 fig.). 



3 p 2 



