806 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Another system of keeping up the circulation is by means of an auto- 

 matic tiltcr. 'iliis apparatus consists of a small balanced table Laving 

 an oscillating motion on a central axis, and made to carry one or moro 

 slides. The slides rest on the table with tho reservoirs at riglit angles 

 to its axis, so that each reservoir may bo raised or dejiressed at intervals 

 of about three hours ; this being about the time occupied for the water to 

 flow from one reservoir to the other when projierly adjusted. The tilting 

 is obtained from clockwork placed in a box underneath. 



The first method has the advantage of simplicity and also of giving 

 a complete change of water, and on that account is jierliaps the best for 

 most organisms. I may say that with a slide of this kind I have liad tho 

 pleasure of watching three generations of Floscularia in succession. 

 These organisms are probably amongst the most difficult objects to keep 

 in a small slide on account of their voracious habits." 



Mr. Beaumont also informs us that a friend who uses one of the slides 

 without any tilting arrangement, finds that all that is necessary is to lay 

 the slide on a flat surface and remove the cover from one of the reservoirs ; 

 this allows free evaporation to take place in the uncovered reservoir, thus 

 setting up a current through the slide. Mr. Beaumont thinks that, on 

 the whole, an arrangement without tilting is preferable, as the organisms 

 are not precipitated against the sides of the cell so much. 



Holman's Current Slide.* — Dr. Holman says that on his slide 

 Protococciis may bo kept alive many days ; Amoeba three weeks ; and 

 Bacteria for six months. In the minute canal, 1/100 in. wide, and 1/1000 

 in. deep, between the two concavities with shallow margins in his slide, 

 blood-corpuscles may bo caused to flow in either direction, to roll 

 over, or to stand on edge by the warmth of the hands of the operator, 

 brought towards the stage of the Microscope at a distance of about six 

 inches. 



Life Slides.f — Dr. A. C. Stokes in studying the morphology of 

 minute animal organisms, uses only a shallow shellac cell, with about 

 one-fourth of the ring scraped from both the upper and the lower 

 margins, thus leaving two curved supports for the square cover, one on 

 each side. This gives the inclosed drop with its animal life plenty of 

 air, and facilitates the application of the wet brush at the point where 

 the square cover projects beyond the lateral cell-wall. The secret of 

 success consists in leaving enough of the cement ring to properly 

 support the cover, and to lessen the force of the inflowing water supply, 

 and also in having tho cell shallow or deep according as the animals 

 are microscopically small or large. Much depends on the depth of the 

 cell in all cases. A comjiaratively large Infusorian, a Eotifer, or a 

 Chsefonotus can be injuriously hampered in its movements and in the 

 proper performance of its functions by a cell of insufficient depth, and a 

 good objective can be greatly hampered in its functions by a cell of too 

 great depth. 



The author also jiroposes the following form : — A small square, cut 

 from glass of any desired thickness, is cemented with Canada balsam to 

 a slip, and surrounded by a thick glass or zinc ring so as to leave a 

 wide space between these parts. On the ring place a ring of wax, and, 



* Journ. New York Micr. Soc, iv. (1888) p. 168. 

 t The Microscope, vii. (1887) pp. 129-33 (3 figs.). 



