718 Henry B. Ward, 



American Society of Zoologists at Minneapolis in 1910 and reported 

 in preliminary fashion in the proceedings of that meeting. After 

 the paper had been presented I learned that my friend and colleague 

 Professor Kofoid of California had reported some work on the same 

 form in a paper the appearance of which in printed form had been 

 greatly delayed (Kofoid and Watson, 1910) and that one of these 

 authors had completed a study of the same worin. This has since 

 appeared in print (Watson, 1911) and forms an important contri- 

 bution to out knowledge of these species and to the interpretation 

 of the structure and relationship of the parasitic Plathelminthes. 



Comparison of my own results with these shows, however, that 

 on some points I am able to furnish further data and to correct 

 Avhat I believe to be errors in Observation or interpretation. 



Historical. 



Wagenee (1852) was the first to study and describe this species 

 from its proper host. He named it Amphiptyches urna and described 

 the anatomy in a manner substantially correct. Since writing my 

 own paper and reviewing the work of intermediate authors I have 

 had opportunity to study the original paper of Wagenee and his 

 work will receive especial mention in the appropriate place. Many 

 of his "errors" which have been "corrected" in later papers are 

 in fact more careful and more precise observations than were made 

 by his followers. Diesing had established somewhat earlier (1850) 

 the genus Gyrocotyle for two parasites supposably from an antelope 

 and a mollusk. Later Wagenee recognized the identity of the two 

 genera and discarded the name he had proposed in favor of the 

 earlier designation. 



Monticelli (1888) was the first to recognize the true relationship 

 of this form, allying it to Amphüina and including both in the 

 Cestoda whereas previous authors had generally assigned it to the 

 Trematoda. Somewhat later (1892) he established the group of 

 monozoic cestodes, the Cestodaria, to include among others the 

 species of Gyrocotyle. 



Spencee (1889) made the first extended study of the anatomy 

 of this form. He described specimens taken from CaUorhynchus 

 antardicus, a Chimaeroid from the seas of the southern hemisphere. 

 Lönnjberg's paper (1891) included a more extensive study of this 

 form than has even yet been made by any one eise and is especi- 



