554 A DESCRIPTION OF THE ENTOZOA COLLECTED BY DR WILLEY 



The most posterior twenty segments or so of this worm were removed and divided 

 into three portions. Each of these was cut into sections in a different plane. The 

 segments at this end were, as was to be expected, mature and the uterus was spacious 

 and crowded with ova in well developed spherical egg-shells. The uterus is single and 

 common to the two sets of generative organs as in Dipylidium and Ctenotaenia. 



When the ova first pass into the uterus it is a branching sac, the numerous 

 diverticula of which are separated by well developed and bulky masses of parenchyma, 

 but as the segments age this parenchyma tends to be absorbed, the partitions it 

 creates between the diverticula of the uterus disappear until in the last stages the 

 uterus is a cavity with practically no subdivisions, an occasional slight strand projecting 

 into its lumen being the only trace of its former irregular shape. 



At this most ancient and posterior end of the animal the enormous development 

 of the transverse canal connecting the two ventral lateral vessels is fully apparent. 

 They have attained so large a size as to equal that of the uterus and the two 

 together form very nearly the whole of each segment, for the walls of both have 

 become very thin. No trace of the small dorsal lateral vessel exists at this end of 

 the animal. At the junction of each transverse vessel with the ventral lateral there 

 is a well developed valve which permits a flow of the fluid contained therein only 

 in the direction from before backward. The valves are very regularly arranged, as is 

 seen in Fig. 24. The only other structures to be found in these posterior segments 

 are the two nerve cords, each very flattened and closely applied to the outer surface 

 of the dorsal lateral canal, and the remains of the genital ducts with their openings 

 one on each side of each segment. The tissues of the body are at this stage very 

 much reduced and the parenchyma is largely absorbed. 



The determination of the .systematic position of this worm is a matter of great 

 difficulty. In the last few years a considerable number of new genera have been 

 established for the tape-worms of Birds. Some of these like the species in question have 

 double genital pores on each proglottis. Amongst these may be mentioned the Cotugnia 

 and Amahilia of Diamare', and the Diploposthe of A. Jacobi-. The specimen Dr Willey 

 has brought home differs from these species in the entire absence of hooks. Both 

 when examined in oil of cloves as a whole and when cut into sections and examined 

 in detail, no trace of a hook was to be seen. However too much reliance must not 

 be placed on this point, for as Professor Railliet has been kind enough to remind 

 me the hooks of the tape-worms of birds are very apt to fall off and are not 

 unfrequently left behind in the host. 



The rostellum of my form is so rudimentary that it can hardly be said to exist 

 at all. Another feature in which this species differ from — at anj- rate — Coturjnia is 

 that the uterus in the older proglottides is a spacious, definitely- walled chamber with 

 nothing but ova in its cavity whereas in the last named species it is " representato 

 da cellette riempite da una massa parenchimatosa in cui si trovano le nova." The 



' Ball. Sue. Napoli, Ser. 1, vii. 1893, p. 9, and Gentrhl. Bakter. xxi. 18'.i7, p. 862 and xxv. 1899, p. 35-2 ; 

 see also Cohn, Zool. Anz. xxi. 1898, p. 557. 



■•^ Zool. Jahrb. Anat. x. 1897, p. 287, and CentrhK Bakter. xxi. 1897, p. 873. The question as to the generic 

 identity or distinctness of tlie last two forms mentioned is discussed in the memoirs here cited. 



