58 ILLINOIS BIOLOGICAL MONOGRAPHS [408 



That Stilesia and Avitellina are quite closely related to Thysano- 

 soma is too evident to need discussion. The exact position of these 

 genera with respect to each other must be left unsettled, however, until 

 the species of Thysanosoma have received more careful study. At 

 present we can do no better than accept Gough's decision (1911) that 

 Stilesia and Avitellina represent a subfamily distinct from Thysano- 

 soma. 



In the subfamily Linstowinae, conditions are unsettled and uncer- 

 tain, owing to the recent efforts of Beddard (1911, and 1912), and 

 others. It seems little short of absurd to decide from external characters 

 (1911:652) as to which of about 20 genera a given cestode should be 

 referred to, the possible list including such genera as Anoplocephala, 

 Zschokkeella, Thysanosoma, Davainea, Hymenolepis, Oochoristica and 

 Taenia. "Within two years, Beddard has actually placed one cestode 

 (whose latest name is Zschokkeella gambianum) in three genera, repre- 

 senting two subfamilies; and there is no assurance that the present 

 disposal is final. Since Beddard has proved his worth as an investigator 

 by his researches in other fields, one might expect better things in the 

 future ; but as yet, while he has dwelt at great length upon the signifi- 

 cance of the size and appearance of sucker and scolex, the presence or 

 absence of a neck, and other such features, he has failed to tell, in any 

 instance, whether the genital ducts cross the excretory ducts dorsally 

 or ventrally, or pass between them; at least, several hours were spent 

 in search in his voluminous articles without finding any information 

 on this point. Bischoff (1912) has likewise contributed considerably 

 towards a state of general confusion in this group. He has added to 

 the genus Inermicapsifer several species, without giving, apparently, 

 any adequate study to each. The few facts that he gives are not suffi- 

 cient in most cases to show that the species exist; and if they do exist, 

 there is no evidence in many cases that they should be placed in the 

 Inermicapsifer group rather than in some allied group. 



In the present condition of affairs, there are no characters except 

 trivial unimportant ones upon which to separate the so-called genera 

 Zschokkeella, Inermicapsifer, Thysanotaenia and Hyracotaenia from 

 each other. My own opinion is that they all belong in one genus, with 

 the exceptions of Zschokkeella remota and Thysanotaenia lemuris which 

 seem to belong elsewhere. In the present condition of our knowledge 

 of most of the species of the group, however, any alterations would 

 merely add to the confusion already existing. "Taenia" anoplocepha- 

 loides must be given a place amongst the Linstowinae, close to the genus 

 Linstowia. Of the genera of the Linstowinae, Linstowia shows, by the 



