interleaved with blank pages to encourage students 

 to draw^ if possible, from the microscope, the necessary 

 diagrams for themselves, for a careful microscopic 

 drawing is infinitely more valuable than a mere text- 

 book description. 



In conclusion, I must add that Dr. Scott's and 

 Professor Farmer's admirable lectures delivered at 

 the Eoyal School of Science have been of great value 

 in drawing up this little work, and that much of 

 the information so gained has been supplemented by 

 personal observation. 



C.M.W.E. 



December, 1893. 





