58 THE MICROSCOPIST. 



The Pleurosigma angulatum (Plate I, Fig. 29), with suit- 

 able power and illumination, should show distinct hexag- 

 onal areolations. The Surirella gemma (Fig. 30) shows a 

 series of fine transverse lines across the ridges which run 

 from the edge to the central line. The finest of these 

 ridges are not always readily seen, and the transverse 

 ones are only to he mastered by toil and patience. 



The Grammataphora subtilissima (Fig. 31) shows trans- 

 verse lines (or rows of dots) along the edge, and sometimes 

 a double series of oblique lines. 



CHAPTER V. 



MODERN METHODS OF EXAMINATION. 



MICROSCOPY does not limit its researches to optical 

 enlargement, but seeks to comprehend elementary struc- 

 ture, and its methods vary according to the object imme- 

 diately in view. It may seek merely to discern the form 

 or morphology of the elementary parts or their peculiar 

 functions. It may be concerned with inorganic forms, 

 normal or pathological anatomy, or with physiology. 

 Each department of pursuit will suggest some variation, 

 yet a general plan of operation is possible. 



Coarse, and moderately- large objects, as a small insect, 

 a piece of vegetable tissue, etc., may be observed by plac- 

 ing it in the forceps, or on the stage of the instrument, 

 under an objective of low power, but ordinarily a consid- 

 erable degree of preparation is needed in order to acquire 

 a true idea of structure. 



Most of the tissues to be examined are in a moist con- 



