ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



845 



finders, shown in fig. 166, in which the 'milled heads a b for the 

 rectangular movements are placed within the circumference of the 



Fig. 168. 



stage. There are two verniers, one of which is shown at n (fig. 164). 

 The rotation of the stage can be stopped by the arm m. 



Fig, 1G7. 



Fig. 165 is substantially the same form of instrument with a 

 screw micrometer eye-piece s and an Abbe spectro-polarizer (Po, 

 Sp, P, Sk, Spl). 



The stage for this form is shown in fig. 167. 



