MAMMALIAN CESTODES. 569 



generative pores and at the middle of the segment ; each ovary- 

 lies in front of the corresponding vitelline gland. The vagina is 

 narrow and passes forward, rnnning in front of and parallel to 

 terminal section of cirrus-pouch ; posteriorly it dilates into a 

 receptaculum seminis lying close to and in front of ovary and 

 behind dilated region of cirrus-sac. Uterus as a simple cavity is 

 absent (?). The developing ova are lodged singly in cavities of 

 the medullary parenchyma, which they nearly fill, and are without 

 any lining epithelium. Eggs with veiy wide but delicate shell. 



From this general resume Ave may now endeavour to form a 

 generic definition of DijjilopyUdmm by eliminating from the a,bove 

 characters those which are in all probability to be regarded as 

 only specific in value. 



Diplopylidium, gen. nov. 



Retractile nvuscular rostellum armed tvith tivo circles of hooks. 

 A double set of reproductive organs in each proglottid. Genital 

 canals j^ciss hetiveen dorsal and ventral excretory tubes. Vagina 

 lying in front of cirrus-sac. Cirrus-sacs large and mtoscular, bent 

 upon themselves : cirrus coiled, very slender, and unarmed ; sperm- 

 duct forms a coil. Testes numerous, filling up available space in 

 proglottid. Ovaries two, in front of vitelline glands. Vagina 

 narrow, loitli receptaculum seminis. Uterus represented by nume- 

 rous cavities, each containing one egg only. 



We have now to consider the afiinities of this tapeworm and 

 the family within which it should be placed. 



There is not a very lai-ge number of genera in which the 

 reproductive organs are double in each segment. We find, how- 

 ever, such forms in nearly all of the families into which the 

 Tetracotylean Cestodes are divided. We may at once place on 

 one side those genera, such as Cittotcenia and Monieza, which 

 belong to the Anoplocephalidas ; for in the genus which forms the 

 subject of the present communication there are not, as in these 

 forms, persistent uteri ; and, moreover, the worms of the family 

 Anoplocephalidfe are not pi'ovided with a hooked rostellum. Nor 

 can we place the present genus, which 1 propose to term Diplo- 

 pylidium, with either Diplophallus * or I)iplop)osthe, two genera 

 which are nearly allied to each other, though placed by Ransom t 

 in separate families, viz. the Acoleidse and Tfeniadse. It must be 

 noted, however, that Fuhrmann %, in his well-known revision of 

 the tapeworms of birds (those belonging to the Cyclophyllidea), 

 regards Biploposthe as not strictly referable to the Tteniadse, but 

 as forming an intermediate type between this family and that of 

 the Acoleidfe. 



* For anatomjf of Diplophallus, see Colin, Zeitschr. vviss. Zool. Ixvii. 1897, p. 277, 

 and Wolfhiigel, " Beitr. z. iCenntniss d. Vogelhelminthen," Inang.-Diss. Freiburg- 

 im-Br. 1898. 



t Bull. U.S. Nat. Mus. 1909, no. 69. 



X Zool. Jahib., Suppl. vol. x. 1908. 



