688 



SUMMABY OF CURRENT RESEARCHES RELATING TO 



Fig. 128. 



polished plate of glass, incased in a brass ring, which clamps on the 

 circular stage. The slide-carrier, which moves on it, consists of a 

 light metallic plate, and has protruding from its lower surface four 

 small points ; at its two ends are prolongations, which are bent 



downward and inward, and, acting 

 as springs, press against the lower 

 surface of the glass. As the con- 

 tact between glass stage and slide- 

 carrier is only in these six points, 

 friction is reduced to a minimum, 

 and the action of the latter, 

 although firm, is smooth and steady. 

 It is claimed that it enables work to be done with far more facility 

 than in the ordinary brass stage, where the entire surface of the slide 

 bears on it, and that it is altogether more agreeable. The slide- 

 carrier is provided at each end with small milled heads for manipula- 

 tion, and has spring clips and a stop for Maltwood finder. 



Thomas' Vivarium. — Mr. C. Thomas has devised a life-slide which 

 is in effect a modification of the Hardy vivarium, enabling it to be 

 readily applied to observations with high powers. With the earlier 

 form, the upper plate is necessarily so thick that it is impossible to 

 use it for the examination of such organisms as the Cilio-flagellata 

 which require the highest powers. 



The new vivarium is shown in Fig. 129, with the two principal 



plates held together by two 

 indiarubber bands, and a 

 segment of another band 

 forming the sides of the 

 cell as in the Hardy viva- 

 rium. The speciality of 

 Mr. Thomas' device is the 

 addition of a third plate of 

 thin glass, contiguous to the 

 upper plate and of about 

 the same size, the latter 

 being pierced with a central 

 aperture. We thus have a cell the upper side of which is thin enough 

 to allow high powers to work through it. The thin glass is so 

 supported by the upper plate, with which it is in contact over the 

 greater part of its surface, that we have found from experience that 

 there is practically no risk of breaking it in putting the cell together. 

 A piece of very thin glass can be placed inside the cell and kept close up 

 to the front by wedging it with a small piece of rolled or twisted paper. 

 The upper plate is made shorter than the lower so that there may 

 be no danger of the plates being pressed together unequally and the 

 thin plate crushed when the apparatus is taken up by one end. 



Bausch and Lomb Optical Co.'s Immersion Illuminator.* — 

 This (Fig. 130) is designed to utilize the full capacity of medium 



* The Company's Price List, 7th ed., 1882, p. 32 (2 figs.). 



Fig. 129. 



