110 SUMMARY OF CURRENT RESEARCHES RELATING TO 



objectives sent to him in regard to their amplifying power, working 

 distance, absolute size of field, and real aperture.* 



Schultze's Tadpole - Slide.t — This slide (or "microscopic 

 aquarium") (Fig. 19) was devised for showing the circulation of the 

 blood or the development of the blood-vessels in the larvge of the frog 

 and triton. To one side of a thick slide is fastened by means of 



Canada balsam a piece of another slide, cut as represented at A, and 

 to the other side a second piece, of the shape seen at A', so that there 

 is a small cell in the centre of the slide, of the form shown in section 

 in the figure. A cover-glass d closes the cell. 



To place the larva e in the cell, the cover-glass is taken off 

 and the larva fished out of the water in a small watch-glass, and 

 poured with the water into the cell. By manipulating with a brush, 

 its head is brought into the hollow of the glass at A, and the tail 

 placed on the sloping surface at A'. The cover is then quickly 

 replaced, care being taken that the cell is full of water. The animal 

 is txclnded from air by the water, which, when it evaporates, can be 

 replaced with the brush. In this way the circulation of the blood in 

 the tail may be observed for hours at a time. 



Stokes' Tadpole-Slide.t— Mr. A. W. Stokes fastens two pieces of 

 a vulcanite ring (Fig. 20) to an ordinary slide so as to form an oval cell 

 iust large enough for the body of the tadpole, the tail projecting 

 through an opening in the cell. Close to the latter a s<iuare of thin 



Fig. '20. 



cover-glass is cemented by Canada balsam so as to raise the tail to a 

 level with the body. On each side of this are cemented two small 

 oblong pieces of thin glass forming a cell for the tail to lie in. A 

 square of cover-glass over the body, and another over the tail, will 

 keep the tadpole in place. 



* North. Microscopist, i. (1881) pp. 253-7. i .o n/i «„ n 



t Thanhoffer's ' Da8 Mikroskop unci seine Anwendung, 1880, pp. 148-9 (1 fag.). 

 X Ann. Rep. Postal Micr. Soc, 1881, p. 13 (1 fig.)- 



