M. Siebold on the Transfo7'mations of Cj/stoid Worms. 431 



was the very individual from which the figure in Lister was 

 taken, as it agrees perfectly in size as well as general contour, 

 and is evidently, from the comparative faintness of its coloration 

 as well as its general appearance, a very old shell. 



XLIII. — Experiments on the Transformation of the Cystoid 

 Worms into Tmiias. By C. T. Von Siebold*. 



1 WAS the first to advance, in the second volume of my ' Manual 

 of Physiology,^ published in 184i, the statement that the cystoid 

 worm which lives as a parasite in the livers of rats and mice (the 

 Cysticercus fasciolaris) was nothing but a stray Tcenia which had 

 become vesicular, and which was in fact the tape-worm of the 

 cat {Tcenia crassicollis) . I also affirmed that the Cysticercus fas- 

 ciolaris, like all other Acephalocysts, never possessed sexual or- 

 gans, and therefore could only propagate by sexual generation 

 when it found a suitable body, where it would lose its vesicular 

 form and acquire the power of sexual development. 



In the experiments made at the Institute of the University of 

 Breslau, these transformations took place, as soon as the liver of 

 a mouse or rat, previously ascertained to contain a Cysticercus 

 fasciolaris, had been devoured by a cat. In the stomach of the 

 cat, the livers of these Rodents were digested, whilst the worms 

 contained in them remained unhurt ; this parasite lost the caudal 

 vesicle filled with fluid, and was then to be seen, without a tail, 

 in the chyme of the stomach and small intestines of the cat, 

 where, finding itself in a suitable place, it became developed 

 in the articulated form of a tape-worm {Tcenia crassicollis) with 

 adult sexual organs. The perfect agreement of the head of the 

 Cysticercus fasciolaris with the cephalic extremity of the Taenia 

 crassicollis, as well as the fact that the different phases of deve- 

 lopment of the latter are often to be met with side by side in the 

 intestines of cats, conducted to the preceding conclusion, which 

 has received the approbation of many naturalists, but the cor- 

 rectness of which is still doubted by others. 



Last year. Dr. Kuchcnmeistei*, of Zittau, made some experi- 

 ments with the Cysticercus pisiformis, which is frequently met with 

 in the cysts of the coats of the intestines of the hare and rabbit. 

 He caused some dogs and cats to devour these cysts, in the hope 

 that after some time they would be developed in the intestines 

 of these animals in the form of tape-worms. This experiment 

 succeeded completely with the dogs, thus confirming that which 



* From the Ann. Sci. Nat. li sev. xvii. p. 3/7- 



