KEW CESTODES FROM THE TASMANIAN DEVIL. 693 



the length caused by a bulging of the walls of the cirrus sac due 

 in its turn to the rapid growth and consequent coiling of the 

 cirrus. When the cirrus sac is in this fully formed condition, the 

 cirrus itself is difterentiated more thoroughly into those i-egions 

 less mai'kedly indicated in earlier stages. The sperm-duct enters 

 the cirrus sac at the apex and its lumen contracts to a fine line 

 for a short space near to its entry. This is particularly obvious 

 in the last few segments of the body, where the sperm-duct has 

 become much dilated before its entry into the cirrus sac, and thus 

 offers a greater conti'ast to this exceedingly nari'ow region. 



In these more mature cirrus sacs the flask-shape has been 

 acquired, as already mentioned. But the neck of the flask is 

 much longer than the body part. The latter is so fully occupied 

 by the coils of the cirrus itself that there is but little of the inter- 

 stitial packing tissue to be seen. At its entry into the cirrus sac 

 and for a considerable time thereafter the duct is thick-walled, 

 with a very narrow lumen, and much coiled. This region of the 

 cirrus is succeeded by a not very long but coiled tract, which is 

 much wider and has thinner walls. The lining membrane bears 

 numerous spinelets. Finally, the distal region of the cirrus is 

 again thick- walled and witli a narrow lumen : it opens into the 

 genital cloaca without any alteration of character. In the most 

 posterior segments of the body the greater part of the cirrus sac 

 is filled with sperm, the posterior region alone showing a group of 

 coils of the cirrus. Whether the anterior part of the cirrus has 

 become ruptured, as it appeared, or has been simply enormously 

 expanded and its walls reduced to extreme tenuity by the enclosed 

 sperm, I am unable to say. 



The systematic position of this tapeworm is difficult to fix with 

 any confidence. The generative system, and, indeed, the internal 

 anatomy generally, presents no differences of importance from 

 many Tetracotylea ; and there are, indeed, no reasons so far why 

 the worm should not be placed in the Anoplocephalidee, which 

 family, as has been pointed out, contains nearly all the Marsupial 

 tapeworms. On the other hand, the very much developed layers 

 of longitudinal muscles in the body-wall suggest the family 

 Acoleidae. The difficulty, however, of accurately placing the worm 

 lies in the peculiarities of the scolex. There is no doubt that it 

 contrasts very considerably with the general form of the scolex 

 among the Tetracotylea in a number of points, of which the 

 principal ones are : — (1) its large size, both relatively to the body 

 and actually ; (2) the presence of numerous grooves which cannot 

 be, at any rate, entirely artefact, as they are converted here and 

 there into tubes running within the thickness of the head ; 

 (3) the relatively minute size of the four suckers and the fact that 

 two of them and two only are furnished with hooks*. 



* Fuvtliermore, these hooks are distinctly hollow at theii- broader end, " like a 

 Ruminant's horn," as Shipley (Willey's Zool. Res., Entozoa, 1900) notes of CaUio- 

 bothrium, one of the Tetraphyllidea. 



