48 



of undertaking the work was two-fold. First, it was thought if 

 its original host could be discovered the disease might be pre- 

 vented to a great degree, and much good result therefrom. 

 Second, the love of original investigation and a determination 

 to work out the life history of this parasite, which, although well 

 known in its mature condition in the trachea of fowls for nearly 

 one hundred years, had thus far, in its embryonic state, remained 

 unknown. The work has been exceedingly difficult, for several 

 reasons. When the investigation was begun, I knew nothing 

 about Entozoa. Microscopical work was also comparatively 

 new. Living in a small village, I had no public libraries to con- 

 sult, and was dependent for the literature of the Entozoa on a 

 few books which I procured during the investigation. My pro- 

 fession also left me little leisure, and the most of this work has 

 been done at such odd times as I could spare from other duties. 

 I wish here to express my thanks to the eminent naturalist, Dr. 

 Joseph Leidy, of Philadelphia, for many favors in inspecting my 

 microscopic slides, and for advice and encouragement in the 

 work. Valuable, indeed, were the services he rendered me. I 

 am under obligations to Lord Walsingham, of England, for 

 books to aid in the investigation. Friends in the Buffalo Micro- 

 scopical Club, and neighbors, have also assisted me in various 

 ways. I have freely consulted Dr. T. Spencer Cobbold's work 

 on Parasites, and Dr. Pierre Megnin, " On the Gapes Disease in 

 Gallinaceous Birds." Finally, I trust these pages will not be 

 scanned with too critical an eye, for, doubtless, imperfections 

 will be found. I can only say that I have honestly endeavored, 

 according to the best of my ability, to place before the reader 

 the life history of one of the humblest of creatures, a worm, but 

 which, nevertheless, plays well its own part in this world of ani- 

 mated nature. 



ZOOLOGICAL CLASSIFICATION AND HABITAT. 



The animal kingdom is divided into several sub-kingdoms. 

 One of these is called Worms [Vermes). This sub-kingdom is 

 separated into classes, one of which is named Round Worms 



