150 PROCEEDINGS OF THE ACADEMY OF [March, 



festations out of fifteen animals examined. One of these was an 

 American gray wolf, which was given a vermifuge. As a result 

 segments were obtained corresponding to those of Tenia marginata. 

 The wolf has been isolated. He could easily have been the source 

 of some of the cases. In others, however, the animals had been 

 housed in a distant building or were newly arrived. They were 

 doubtless infested when they arrived. 



One of our cases has furnished a monster formation. The cysts 

 usually consist of a single bladder, into which the head is invaginated. 

 By pressing upon such a cyst the head and long narrow neck may be 

 expressed. In the monster forms the cyst is invaginated by a 

 second cj^st, and into this second cyst the head is invaginated so that 

 when pressure is applied two elongated necks emerge, the innermost 

 bearing the head. The formation is discussed by Railliet, p. 238. 



If these cysts be ingested by a canine, the bladder will be destroyed, 

 the head becomes fastened to the intestinal wall and gives rise 

 ultimately to the stroliile, Tcenia marginata. 



The material which forms the basis of this communication has been 

 obtained from the Garden of the Philadelphia Zoological Society, 

 from the Laboratory of Comparative Pathology of which it is reported. 

 During the work I have often had occasion to confer with Dr. Allen J. 

 Smith. The reconstructions of Tropidocerca contorta were only 

 made possible by his generous tender of apparatus and materials 

 from the Department of Comparative Pathology and Tropical 

 Medicine at the University of Pennsylvania. I acknowledge with 

 sincere thanks his freely given advice and criticism. 



Bibliography, 

 CoBBOLD, Transactions of the Linnean Society of London, II, part 8, 1883. 



pp. 357-361. 

 DiESiNn, Revis. d. Nemat., pp. 673, 674. 



Syst. Helminth., II, p. 207. 



V. Drasche, Verhandlung. d. k. zoojog. bot. Gesellsch. Wien, 1883, pp. 114, 11-5. 

 Leuckart, Troeschel's Archiv f. Naturg., 1860, II, p. 135. 

 Leidy, Proc. Acad. Nat. Sci. Phila., 1886, p. 308. 

 LiEBERKtJHN, MuUer's Archiv f. Naturg., 1855, pp. 314-355. 

 V. LiNSTow, Troeschel's Archiv fiir Naturg., 1877, pp. 5, 6. 



Troeschel's Archiv fiir Naturg., 1876, I, pp. .5, 6. 



iirchiv f. Naturg., 1879, p. 175. 



MoLiN, Sitzungsbericht d. k. k. Akad. der Wisse.n., Wien, XXXIII, p. 298; 

 XL, p. 342. 



Denkschr. d. k. Akad. der Wissen., Wien, XIX, pp. 297-299. 



Railliet, A. Traits de Zoologie Medicale et Agricole. 2e Edition. 

 ScHLOTTHAUBER, Aiutlicher Bericht deuts. Naturforscher u. Aerzte, Gottingen 



1854, p. 129. ^ ' 



Description of Plate IV. 

 Fig. 1. — Male Tropidocerca contorta, with the longer penis projected. 

 Fig. 2.— Male T. contorta, with penis retracted. The root of the longer penis 



reaches almost to the head. 



