NEW AVIAN TAPEWORM. 209 



of which I have lately given an account to this Society *. In the 

 foraiei- type, as will be seen in Dr. Gough's paper referred to, the 

 cirrus sac contains a narrow cirrus which is protrusil)le from 

 the sac and is of pretty well the sauie dimensions, through tiie sac 

 not being nt all wider at its free extremity. In Anoplotmnia the 

 cirrus-appai-atus is divi<led into two regions ; there is distally a 

 protrusible sac of much greater calibre than tlie slender cirrus 

 which is continuous with it posteriorly. The protiusible sac 

 appears to be an ingrowth into the cirrus sac of the cloaca geni- 

 talis. It is this kind of tei'minal male apparatus which we find 

 in the tapewoi-m which forms the subject of the present com- 

 munication to the Society. I have examined into its structure 

 both by transverse and longitudinal sections, and have found that 

 it presents certain differences from the cirrus sac of Anojjlotmnia. 

 It has already been said, in describing the cloaca genitalis, that 

 the end of the cirrus sac protrudes into that cavity ; how far it 

 can be protruded witliout any further temporary dislocation of 

 its parts I do not know. It is evident, however, that, as with 

 xinoplotcHHia, so in Otidito'.nia, there is a terminal section of this 

 apparatus which can be protruded, though I have not met with 

 specimens in which the protrusion is actually effected. Text- 

 fig. 27 (p. 206) shows a longitudinal section through a cirrus 

 sac that is seen in a transverse section of the proglottid con- 

 taining it. It will be seen that the whole oi-gan is of con- 

 siderable size, thougli not so large proportionately as it is in 

 Anoplotcunia. It is, however, of much the same shape, being a 

 slightly elongated sphere, though flask-shaped when fully retracted. 

 The sperm-duct in this particular specimen approaches the cirrus 

 sac from one side, and then sharply curves to enter it. The point 

 of entry is at the extreme poster'ior end, i. e. that furthest removed 

 from the oriiice of the cirrus sac into the cloaca genitalis. 



The sperm -duct is a good deal coiled within the cirrus sac and 

 has clear slightly stained walls. It does not, however, become 

 enlarged anywhere to form a vesicula seminalis. The transition 

 between the sperm-duct and the cirrus is abrupt. Tlie cirrus is 

 not, however, of greater calibre, or at most of very slightly greater 

 calibre, than the sperm-duct with which it is continuous. The 

 abruptness of the ti-ansition lies in the fact that the walls of the 

 cirrus are thick and very deeply stained and the lumen propor- 

 tionately reduced. The cirrus is very much shorter than the 

 section of the sperm-duct which lies within the cirrus sac ; it is 

 slightly coiled. The cirrus itself again terminates abruptly in a 

 wider sac. As will be seen in text-figure 27, this latter sac is 

 flask-shaped, and, in fact, broadly corresponds in outline with 

 the entire cirrus sac. The wider part of the flask lies within the 

 wider part of the cii-rus sac and the narrower part in the neck 

 of the latter. 



The whole sac is composed of a deeply staining epithelium, 



* P. Z. S. 1911, p. 1003. 

 Piioc. ZooL. See— 1912, No. XIV. 14 



