330 SUMMABY OF CUEEENT EESEAEOHES EELATING TO 



A plate is given showing the appearance with the apparatus of 

 human red and white blood-corpuscles, red blood-corpuscles of a frog 

 with two vacuoles, and a section through the cornea of Hydrophilus. 



Apparatus for Examining the Reflex in the Compound Eye of 

 Insects.* — Mr. B. T. Lowne has found the best method of examining 

 the reflex to be the substitution of a reflecting ophthalmoscope for the 

 eye-piece of the Microscope. 



By this means a bright luminous spot may be observed as a real 

 image in the tube of the instrument. A 1/4 in. objective must be 

 used, and the mirror of the ophthalmoscope must be strongly illu- 

 minated. The Microscope is then focused so that a real image of the 

 corneal facets is seen between the objective and the eye of the observer. 

 By bringing the object-glass gradually nearer to the insect's eye, 

 the reflex will come into view. The reflex appears as a disc having 

 a fiery glow, in moths, and as a bright ruby spot in the cabbage 

 butterfly. Sometimes six spots, surrounding a central spot, are seen 

 in the eye of the insect; perhaps these are diffraction-images. A 

 similar appearance is seen when the eye of this insect is observed by 

 the naked eye, except that the spots are black. The central spot is 

 always opposite the eye of the observer, whatever the position of the 

 eye of the insect. The reflex seen with the micro-ophthalmoscope is 

 green in Tipula, and bright yellow in the diurnal flies. Coloured 

 diffraction-fringes are usually present around the central bright spot 

 in both these insects ; but the central image is sometimes surrounded 

 by a perfectly black ring. 



Thoma's Frog-plate.f — In addition to the Microscope described 

 supra, p. 309, Professor E. Thoma previously devised and strongly 

 recommended the following apparatus for examining the circulation 

 of the blood in the tongue of the living frog. It is more especially 

 intended for obviating the effects of evaporation by keeping the 

 tongue flooded by the constant passing over it of a rapid stream of 

 salt solution, which at the same time keeps it free from impurities 

 which might interfere with the observations. It also allows the salt- 

 and-water contents of the tissues to be increased or reduced, and the 

 action of other solutions, such as indigo-sulphate of soda, to be 

 observed. 



The apparatus consists of a double plate a of brass and vulcanite 

 (the latter beneath) with an aperture at 6 closed by a sloping block 

 of glass for the tongue to lie on. At e e' are two movable supports 

 for the irrigation tubes. When the Microscope is inclined the fluid 

 is retained by the ledge ccc which surrounds the glass block, passing 

 away through the two tubes dd at the lower end. At the upper end is 

 a support / for the tube used for infusing fluids into the blood, so as to 

 prevent it being displaced if the stage-plate should be moved. Small 

 cork plates are inserted behind the glass block to which the tongue 

 is fixed. 



• Trans. Linn. Soc. Lond.— Zool., ii. (1884) pp. 389-420 (4 pis.). Of. Amer. 

 Natural., xx. (1886) pp. 90-1. 



t Virchow's Arch. f. Path. Anat. u. Physiol., Ixv. (1875) pp. 36-47 (1 pi.). 



