114 ENTOZOA. 



ticercus itself. According to Leuckart, remnants of the caudal 

 vesicle maj be seen after the expiration of an entire day. After this, 

 the young tapeworm grows rapidly, and on the second and third 

 days it displays well-marked indications of segmentation. It has 

 now acquired the length of half an inch or more, and at the twelfth 

 day is fully fom* inches long. Considerable variation in length, 

 however, is not unfrequent, partly owing to the circumstances above 

 mentioned, and partly to the degree of contraction or extension of 

 the body of the worm itself. So far as my observation extends, 

 the joints become sexually mature about the twentieth day, but I 

 believe this condition may take place at an earlier period. 



The facts above recorded in relation to the development of 

 Tcenia s errata from Gysticercus pisiformis are principally due to the 

 investigations of Leuckart ; but the experiences of Kuchenmeister, 

 Van Beneden, Eschricht, Haubner, EoU, Mliller, and others, con- 

 firm, in various ways, the correctness of the data here set forth. 

 My own experiments have produced very similar results ; and if 

 they have done nothing else, they have, at least, satisfied me that 

 Yon Siebold's opposition to the generally-received opinion — as to 

 jT. serrata being quite distinct from T. cmnurus, T. solium, and T. 

 crassicollis — is altogether a mistake. The same may be said in 

 regard to the still more recent doubts thrown upon this subject by 

 the honestly-conducted inquiries of MM. Pouchet and Verrier, 

 who, however, have not been able to set aside the explanations 

 ofPered by Van Beneden as to the circumstances which prevented 

 their arriving at a satisfactory result. Without any hesitation, it 

 may be truly affirmed that the developmental phenomena above 

 recorded, are, in the main, absolutely correct, and, therefore, before 

 quitting this subject, I am induced to offer, as it were, a recapitu- 

 lation of the facts, in the form of a synoptical table. The phases 

 of existence in the life-cycle of Tcenia serrata may, I think, be 

 usefully expressed in the following manner ; — 



