PREFACE 



Professor Leidy for some time previous to his death had in con- 

 templation the publication of a work upon Helminthology and 

 Parasitology. As is well known, for many years he was the 

 only American naturalist who devoted any considerable time to the 

 study of parasitology. 



To students engaged in similar lines of investigation no apolog}^ 

 is needed for the present volume. The subject-matter which forms 

 the basis of the edition consists of verbal communications, short 

 papers, and elaborate memoirs which have appeared from time to 

 time ( 1 845-1 891) in the Proceedings and Journal of the Academy 

 of Natural Sciences, Philadelphia ; the Transactions of the American 

 Philosophical Society, the Smithsonian publications, and scientific 

 journals. 



The material has been arranged serially as it appears from the 

 author's pen ; no attempt at classification could be made without 

 destroying the character of the work. It was a long time before 

 the editor could be induced to undertake the preparation of such a 

 publication ; frequently he was tempted to place his pen aside, 

 knowing full well that Professor Leidy had very little sympathy for 

 compilations. The frequent and constant requests from investiga- 

 tors along similar lines of scientific research, however, for detailed 

 information of the work under consideration has induced him to 

 forego any personal feeling in the matter and allow the work to go 

 forward. 



For the use of students the editor has appended a working bibli- 

 ography of Professor Leidy' s contributions to science. Although 

 care has been taken in its preparation, for any omission that may 

 be found the editor asks the indulgence of the reader. 



Joseph Leidy, jun'. 



