ANATOMY OP CESTODES. 191 



the intermediate host. There is no known exception to this, 

 if we exclude the Ichthyotamiids from the Cyclophyllidea *• 



I direct attention to the annexed text-figure (text-fig. 8), 

 which represents a portion of a horizontal section through a 

 ripe proglottid of Dasyurotcenia robusta. It will there be seen 

 that a very definite orifice on to the exterior runs from the uterus 

 and also from the adjacent ventral water-vascular tube. There 

 is here no question whatever of a rupture due to pressure and 

 the consequent formation of a lateral orifice. The inflection of 

 the layers of the body, and the mode of communication with both 

 the water- vascular tube and the uterus, seem to me to be decisive 

 upon the matter. It is possible that the numerous obstructions 

 upon the course of the water- vascular vessels which I have 

 referred to above, permits of an opening of this kind without 

 undue pouring out of the fluid contained in those vessels ; besides, 

 any opening of the uterus on to the exterior in this region would 

 seem necessarily to involve the vascular tubes. As to the 

 uterine opening, we note that it is lateral instead of dorsal or 

 ventral as is the case in those Cestodes where a separate uterine 

 orifice occurs. In view of the remarkable characters of the scolex 

 of Dasyurotcenia which render its inclusion in any of the 

 recognised groups of the Cestodes difficult (as I have already 

 pointed out in my. original paper upon the genus), it is interesting 

 to observe this difference. 



The uterine orifice lies on the side remote from that which 

 bears the genital orifice ; these latter orifices are unilateral. 

 While there can be, as I think, no doubt that the uterine pore is 

 a preformed orifice, and not an accidental tear such as occurs, 

 but on the ventral surface, in various tapeworms belonging to 

 the Tetraphyllidea, I have not by any means been able to prove 

 its universal occurrence in mature proglotticls. Indeed I have 

 only twice found these lateral orifices. In three other pieces 

 of the same tapeworm (whether of different or the same 

 individual I have no means of knowing) I have seen no such 

 openings, at most a process of the lateral water-vascular vessel 

 deflected towards the periphery. But, on the other hand, I have 

 observed them in one segment in two other pieces of worm. 

 This, however, is not necessarily an argument against the 

 normality of the occurrence, though it does not fully prove that 

 the formation of these pores is normal. It is at least clear that 

 they may be formed. 



* See Beddard, P. Z. S. 1913, p. 256 et seq. 



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