workers that the time spent over diatoms for the pur- 

 pose of studying objectives is well applied, and the 

 most expert manipulators have acquired their exper- 

 ience in this manner. An objective which works well 

 on diatoms works equally well on other objects, and 

 therefore the manipulative skill which has been 

 attained on the former is as well applied on the lat- 

 ter. At the outset work may be done on other 

 objects than diatoms, and where ordinary working 

 objectives, such as a Student 1 inch and J inch, or f- 

 and | inch comprise the outfit, the road to good manip- 

 ulation may be as short as with diatoms The condi- 

 tions in both cases remain the same ; but it must be 

 cautioned that, if histological preparations be used, 

 only such be selected as are reliable. A poor speci- 

 men is perhaps as bad as none at all ; an abnormally 

 thick one obstructs light, makes it impossible for the 

 objective to penetrate through the various layers, and 

 leaves the impression that the latter is defective 



Photo-Micrography. This subject does not 

 properly belong within the scope of this book, but 

 there are some points connected with it which may 

 be of value to mention. 



Any person desiring to do this work should 

 endeavor to obtain some experience in ordinary pho- 

 tography and proper developing. First, as good 

 results in photography with the microscope are diffi- 

 cult to obtain, even with previous experience, a book 

 devoted to this purpose should be well studied before 

 attempting to obtain results. The beginner in this 



