The Microscope. • • 15 



which do not always work well, though in favor with many, serve 

 only to render the worker more dependent. The instrument should 

 be low set, so that it can be used without the necessity of one's ris- 

 ing from the chair or craning the neck to a point of inconvenience 

 if not of pain. Many stands are provided with a hinge, by means 

 of which the body of the instrument may be inclined at any angle, 

 thus obviating the neck-craning act. When working with fresh 

 specimens, however, the stage cannot be inclined, and it is just as 

 well not to use the hinge at all. An achromatic substage condenser 

 is now considered indispensible, particularly in bacteriological 

 investigations. The Abbe condenser, made by Zeiss of Jena, is the 

 best known of these, but the writer has examined one made on the 

 same principle by Bausch & Lomb, of Rochester, N. Y., which is 

 fully the equal of the foi'eign make. 



Lenses. — In ordinary histological work it is not neeessaiy to 

 employ very high powers. One should always use the lowest power 

 which will enable him to see the details of the object he may desire 

 to study. As the high-power objectives are very expensive, the 

 worker can, therefore, dispense with them until he has reached a more 

 advanced point in the study of histology. Two eye-pieces, A and C, 

 and three objectives, 1 in., ^ in. and I- in., will make a serviceable 

 set. The addition of an J- in. objective to the above will furnish 

 any power required for ordinary work. Do not buy cheap lenses 

 with the idea of getting a bargain. Buy the best you can aflPord. 

 So important is this matter of good lenses, that the beginner will do 

 well to consult an expert before purchasing. 



(To be continned. ) 



RUDIMENTS OF PRACTICAL EMBRYOLOGY, BEING 



WORKING NOTES, WITH SIMPLE METHODS 



FOR BEGINNERS.* 



W. p. MANTON. 



TN the following articles a few tried and practical methods for 

 -*■ preparing embryos for microscopical examination will be offered 

 the student. 



Embryos are so easily obtained that even in our largest cities 

 there need be no dearth of material ; and the short account of the 

 development of the domestic fowl, with which these articles will be 

 brought to a close, will give the beginner an idea of what he ought 

 to see. 



♦Copyright, 1888. 



