10 ILLINOIS BIOLOGICAL MONOGRAPHS [298 



favor for general acceptance as does that by Liihe. In 1900 Ariola brought 

 out his revision of the family of the Bothriocephalidae, which, however, was 

 shown by Liihe (1901) to be rather of the nature of a compilation, in- 

 volving at the same time several omissions, than a distinct advance in our 

 knowledge. In 1901 there appeared in Lankester's Treatise on Zoology 

 Benham's classification of Cestodes which professedly follows the earlier works 

 of Railliet and Blanchard. Llihe's (1902a) revision of the bothriocephaUd 

 system comes next in order. It is this newer system, only slightly modified 

 in 1910, that is accepted by the writer with several necessary modifications 

 which are dealt with below. 



From 1902 until Die Siisswasserfauna Deutschlands was published, the 

 literature on the group consists mostly of papers on individual species or mere 

 listings. Spengel's (1905) paper on Die Monozootie der Cestoden ought, 

 however, to be mentioned, since it is one of the latest discussions of a question 

 which occupied a good deal of the attention of many of the older writers. 

 Finally Ward (1910) and the writer (Cooper, 1914a, b) made the latest addi- 

 tions to the American literature, while Stiles and Hassall won the gratitude of 

 the younger workers at least by their pubhcation of the section of the Index- 

 Catalogue of Medical and Veterinary Zoology on Subjects: Cestoda and 

 Cestodaria which the writer has found of inestimable value in the pursuit 

 of his studies. 



EXPLANATION OF TERMS 



Owing to the fact that not a little confusion exists in the earhest Uterature 

 regarding the terms of orientation used for the cestode body, the writer wishes 

 here to explain those that wall be employed in the specific descriptions below. 



Even much later than the time of Diesing (1850) the word "lateral" was 

 used to refer to the flat surfaces of the typical strobila, while "marginal" was 

 and is even yet perfectly clear in meaning; but from the standpoint of bilateral 

 symmetry both words may mean the same thing. Here they are considered 

 to be synon}Tnous and are used to refer to any part which is situated in or at 

 the edges of the strobila and consequently of the individual proglottides. On 

 the other hand, the word "surficial" is adapted from geology to take the place 

 of the word " flachenstandig " which is used freely in Liihe's papers to mean that 

 the structures in question are located on the broad, flat surfaces of the chain. 

 As is customary, the latter are considered to be dorsal and ventral in position, 

 the ventral surface being that which is nearer the isthmus of the ovary. The 

 end bearing the scolex is called the anterior end and the opposite, the posterior 

 end, despite differences of opinion as to which is which. For the sake of brevity 

 the words, "length," "depth" and "breadth" (or "width") are used instead 

 of the longer terms, diameters in the longitudinal, in the dorsoventral and in the 

 transverse directions, respectively, excepting where the organ in question, e.g., 

 the transversely elongated cirrus-sac of the Triaenophorinae, is so shaped that 

 it would be confusing to speak of its obvious length as its width. Otherwise 

 the usual terms of orientation are employed. 



