INTRODUCTION. 



of the illustrations exhibit various degrees of imperfection in some of the 

 details, due to exaggeration of defects in the original drawings, which the 

 artists, without any knowledge of the subjects, have attempted closely to 

 imitate. It has long been a matter of regret to me that I have not been 

 able to secure the services of accomplished artists, educated for the special 

 purpose to give us faithful and beautiful representations of natural-history 

 subjects, such as we so frequently see in the scientific periodicals and other 

 works especially of Germany and France. 



I think it worth while to embrace the opportunity of informing students 

 that microscopic observations, such as those which form the basis of the 

 present work, do not require elaborate and high-priced instruments. Such 

 a microscope as is made by Zentmayer of Philadelphia, Beck of London, 

 or Hartnack of Paris, and sold at prices ranging from $50 to $100, 

 answers all ordinary purposes. The instrument should be furnished with 

 two objective powers, of which the higher should be at least Jth or -1th of 

 an inch focus. A still higher power being occasionally required, I have 

 found an £th or ^th objective of great service. I have now in use a 

 little instrument of Beck, called the Economic Microscope, with 1-inch 

 and J-inch object-glasses and two eye-pieces, sold by W. H. Walmsley, 

 No. 921 Chestnut street, Philadelphia, for $50. An important addition to 

 the instrument, for measuring, is a micrometer, divided into fractions of a 

 millimetre, which may be purchased for a couple of dollars. 



I give the above statement, not with any disposition to detract from 

 the value of the various magnificent microscopes so much in vogue, but 

 with the object of dispelling a common impression widely prevalent, at least 

 among those with whom I habitually come into contact, that the kind of 

 work such as I now put forth can be done only with the help of elaborate 

 and expensive instruments. 



In aid of my researches among the Rhizopods of the Rocky Mountain 

 Region I acknowledge the services of my friend Dr. J. Van A Carter, for- 

 merly of Fort Bridger, now of Evanston, Wyoming Territory. It was not 

 only under his hospitable roof that I was enabled to pursue my investiga- 

 tions, but he conducted my expeditions into the Uinta Mountains and other 

 places to collect materials, and withal defrayed the expenses of our trips 

 Dr. Carter, in his appreciation of scientific matters, has been of eminent 

 service to geologists and other naturalists visiting his region of country. 



