MICROSCOPIC OBJECTS. 69 



without any trouble in preparation, to be examined by the 

 " Standard Microscope" hereinafter described. It may be 

 remarked here, that for examining this class of animals 

 with facility, the mechanical part of the microscope 

 should, as in that instrument, be so constructed as to 

 revolve about its stem ; by such contrivance vessels of 

 any length can be employed without removing the zoo- 

 phytes from them, and thus a series of observations can 

 be made with ease. When the creatures are marine zoo- 

 phytes and require a fresh supply of sea water occasion- 

 ally, the glass vessels with their contents can be kept in 

 a pail of sea water, and thus a fresh supply is given 

 without disturbance. In this manner the functions of 

 these vegetative animals, and the manner in which they 

 seize and devour their prey, can be readily observed. 



The polypidoms or cells formed by these creatures 

 are excellent opaque objects under low powers, especially 

 the genera Flustra, Sertularia, and some others mentioned 

 in the Catalogue. The living masses of CristateUa, often 

 found in clear running ditches, are interesting microscopic 

 objects. — ^The magnifying power required for this class of 

 animals varies from 25 to 100 diameters. 



Vegetable. — ^The vegetable kingdom furnishes the 

 microscopist with a large amount of employment. His 

 researches are not confined to objects of high culture, but 

 the wild and diminutive often present a larger amount 

 both of instruction and amusement than the most choice 

 and highly cultivated. For this reason the author has 

 been obhged to exclude from the Catalogue some sub- 



