OKIGIN OF CYST1CA AND CESTOIDEA. 61 



produced from tlie transversely wrinkled anterior part of the body. 

 In three months these Tcenice attain the length of from twenty 

 to thirty inches and more. 1 In such Tcenice the posterior joints 

 seem to have reached their full sexual development. In some of 

 these tape-worms the last joints become cast off, a proof of their 

 having attained their sexual maturity. The eggs contained in 

 the fully formed joints are perfectly developed, and contain an 

 embryo, furnished, in the usual manner, with six moveable hooks. 



After having thus obtained sexually developed Tcenice, that is 

 to say scolices with sexually matured proglottides, from the 

 Cysticercus pisiformis, I was enabled to decide to which species 

 of tape-worm these scolices, as the head end, and the proglottides , 

 as joints, belonged, and I recognised in them the Tcenia serrata, 

 which had long been known to infest the intestine of dogs. The 

 form of the head, the number, shape, and arrangement of the 

 hooks encircling the head, the construction of the joints, and of 

 the sexual organs within them, the form of the developed eggs, 

 all persuaded me that I had educed the Tcenia serrata out of the 

 Cysticercus pisiformis. 



Perhaps .some of my readers may doubt the conclusion I drew 

 from the above-mentioned experiments, and may object How 

 could T be sure that the dogs which I fed with the Cysticerci 

 might not have come by the tape-worms known as Tcenia strrata 

 in some other manner ? This objection occurred to myself, and 

 all the more strongly since in searching the intestinal canal 

 of dogs fed with Cysticercus pisiformis I often met with 

 thread-worms and tape- worms of another kind (Tcenia cucume- 

 rina), among individuals of Tcenia serrata. So that the question 

 naturally arose whether, in the same way as individuals of the 

 dog's thread- worm (Ascaris maryinata), and the ordinary dog's 

 tape-worm (Tcenia cucumerina], had found their way into the 

 intestine of the dogs experimented upon, so these individuals 

 of the other rarer tape- worm (Tcenia serrata) might not also have 

 arrived there without any assistance of mine. I can, however, 

 bring forward the following demonstrative evidence to substantiate 

 my assertion, that the individuals of Tcenia serrata which I dis- 

 covered in the course of these experiments were really produced 

 from Cysticercus pisiformis. I have repeatedly searched the 



1 With regard to these different stages of development, see the figures in Lewald's 

 ' Dissertation/ cited above. 



