74 DU. F. E. BEDDARD ON THE 



perhaps does not bear any relation to the rostellum of other 

 Cestodes. Related genera belonging to the same division of the 

 Cestodes {i. e. Pseudophyllidea) throw no light upon this question. 

 It is true that an apical depression has been described in other 

 genera ; but where this has been carefully investigated it would 

 appear to be produced simply by an apical fusion — or nearly com- 

 plete fusion — of the lateral bothria. Thus, in Bothriomonus* , the 

 presence of a dividing septum shows that the apical vertical slit 

 is merely the abbreviated remains of the two bothria. Were the 

 septum absent the homology of the depression in question might 

 be more doubtful ; I therefore believe this apical sensory (?) organ 

 to be new to the Pseudophyllidea. 



Text-fisfure 1. 



"^ 



/ 

 C 



A transverse section through the apex of the scolex of Duthiersiafimhriata. 

 c, cuticle ; s, apical sense-organ. 



While I found this structure in examples of Duthiersia from 

 Monitor niloticus, I examined other specimens of Duthiersia in 

 vain. 



Two series of transverse sections of the scolex of specimens 

 from Jlouitor hengalensis showed absolutely no trace of the organ. 

 As these were much larger scolices, the probability of my having 

 failed to recognise the organ is thei-eby reduced. I have in fact 

 little doubt that the apical pit is in those specimens quite un- 

 developed. A comparison in other ways between the specimens 

 from the two species of Monitors showed plainly that we have 

 here to deal with two undoubtedly distinct species of Duthiersia. 



* Cholodkovsky, Annuaire Mns. Zool. de I'Acad. Imp. Sci. Petrograd, xix. 1914, 

 p. 520, figs. 6, 7. 



