AVIAX CKSTODES. 443 



and I aermicapsifer and Davainea, with many " egg-capsules," on 

 the other. In these instances the loss of the i^ostellar hooks would 

 need the reference of Davainea to either Zschokkeella or Ine^-mi- 

 capsifer, and of Icliogenes to Rhahdometra or one of its near allies. 

 The relation is quite like that between Tceniarhyncha (sens, strict.) 

 and Toinia. In Tceniarliyncha, a genvis formed to include the 

 hookless Tcenia saginata, we have a typical Tcenia, differing only 

 by the character mentioned and the correspondingly reduced ros- 

 tellum. It is, therefore, very important to ascertain positively 

 the presence or absence of rostellar (and other) hooks in view 

 of the above relations. This task is — my experience with 

 Chapniania teaches me — not always easy. I have carefully 

 i-e-examined the scolex of my species Zschokkeella gambiana in 

 order to set doubts at rest. I am still unable to find hooks 

 thereon, and cannot, therefore, alter my opinion of its systematic 

 position. 



Pnoc. ZooL. >Soc.— 1915, N"o. XXXI. 31 



