TAPEWORM, DRSPANIDOTAENIA SAGITTA. 277 



from the papillae seen in the polar axes of the eggs of either 

 Eymenolepis murina (Weinland) or those of Trichocephalus dispar. 

 There is some affinity, however, with the latter, as the papillae 

 of the former are the elongations of the embryonic membrane 

 alone, and do not affect the shell. Neither is it comparable to 

 the lid-like operculum of Bothriocephalus latus, but, as will be 

 seen on reference to Figs. 7 and 8, it is a simple catch -spring 

 arrangement of the shell. 



In the determination of a new species of tapeworm, much 

 depends on the character, number, length, and divisible length 

 of the cephalic hooks — that is, if the creature is one of the 

 armed species; but if unarmed, then the structural formation 

 and anatomy, both external and internal, must be carefully 

 studied and compared with other known species, so as to arrive 

 at a definite conclusion. In the first case, although the hook 

 must necessarily play an important part in arriving at a con- 

 clusion as to the species under consideration, still the case is at 

 all times strengthened if proofs can be adduced of the dissimilarity 

 in the anatomy of the species in question from any other known 

 tapeworm. In this instance, as I have already mentioned, I 

 have but one hook to guide me to defining the species; still, this 

 hook, plus the number, is so dissimilar in divisibility of length 

 and character from any other of the Drepanidotaenia (Railliet) 

 as to give it a distinctive character. 



Externally, the four oval suckers (Fig. 1) are so placed round 

 the pyriform scolex as to give the head an arrow-like or sagittal 

 appearance ; that is to say, their proximal ends are attached to 

 the base of the scolex, whilst their distal ends stand out promi- 

 nently from the sides of the head. On the proximal lateral 

 border the genital pores are not bossed, as one so often finds 

 them in avian tapeworms, but are situated in depressions or 

 cavities. These are all external characteristics. In its internal 

 anatomy the spatuliform monotestis is somewhat remarkable, but 

 otherwise there is little in the genitalia that calls for comment. 

 The six-hooked brood, or hexacanth stage, however, cannot be 

 so easily dismissed, as I know of no ovum — neither can I, on 

 reference to the literature at my disposal, find one — with the 

 catch-spring arrangement possessed by that of this species. This 

 character, taken in conjunction w T ith the hooks and the formation 

 of the scolex with its suckers, strengthens the decision I have 



