CHAPTER XVI 



MICROSCOPIC PREPARATIONS IN MARINE ZOOLOGY 



REQUISITES. A microscope ; preferably a short-tubed, 

 Continental pattern one, that can easily be used vertically, 

 with objectives of different powers viz. (in English method 

 of expressing powers) 1 -inch, J-inch, and J-inch these will 

 suffice to begin with. 



The lowest of these is suitable for viewing small objects 

 in their entirety. The highest (J-inch) will be sufficient 

 to reveal the majority of infusorians, the cells, collars, and 

 flagellse of sponges, sting cells, etc. quite enough for the 

 present purpose. 



A microtome. The form and quality of this must be 

 regulated by matters pertaining to the exchequer. They 

 range from a few shillings to many pounds. 



In some the object to be cut into sections is cemented 

 to a little table, which can be moved to any angle, and the 

 razor blade works across it mechanically ; in others the 

 blade is fixed, and the object fastened to a support is ad- 

 vanced to a regulated measure and brought down to the 

 blade ; in others there is a well, in which the object is em- 

 bedded in wax or other medium, and the bottom of this 

 well raises the column of wax and its contained object to 

 the cutting level, a smooth brass plate, across which the 

 razor is moved by hand. 



For general, all-round work one of these is best, and they 

 are not expensive. I will suppose we are using one of these. 



It must be made so as to screw firmly to the edge of the 



316 



