CYSTICERCUS TENUICOLLIS. 391 



not quite clear. The observation of Lebert, who sometimes 

 found a rudimentary peduncle upon them, is in favour of their 

 having been primarily pedunculated processes similar to those to 

 which we have just referred, with only the single diffei'euce that 

 they do not remain attached and burst in that condition. A 

 third mode of generation, which only occurs in EchinocGCCUs 

 altricipariens, has been observed by Yirchow and Luschka in the 

 human body. It occurs, however, only in those specimens of 

 this Echinococcus which intrude themselves into vacuities in the 

 tissues and the interior of vessels (blood-vessels and lymphatics) 

 in the form of cylindrical tubes. Within these narrow cylin- 

 drical tubes various vesicular appendages, furnished with filiform 

 peduncles, are formed, which then probably become separated by 

 constriction and form closed vesicles. These appendages, or 

 vesicles separated by constriction, can then proliferate again, or, 

 which appears to be the most usual occurrence, they remain 

 barren, and become Acephalocysts. The colonies are mixed, 

 actually proliferating in the mother-vesicle, and in certain 

 daughter-vesicles, but usually sterile in the parts separated by 

 constriction ; although I do not believe it to be impossible for 

 the latter to proliferate. In them, therefore, we have, — simple 

 scolex-formation, ordinary formation of daughter-vesicles, and 

 regeneration of so-called daughter-vesicles by the constriction of 

 particular buds or by a sort of fission. The latter, however, 

 is only a slower and more distinct process, occurring in the 

 cylindrical diverticula of an Echinococcus-colony , of that mode 

 of formation by which the daughter-vesicles are produced, and, 

 according to Lebert, frequently pedunculated. The most im- 

 portant distinctive indication of this mode of generation lies 

 in the products which sometimes thus originate. Such 

 vesicles, when completely constricted, may again become inde- 

 pendent colonies (Echinococcus- or Acephalocyst-sacs), which 

 are totally unconnected. It would, therefore, be erroneous to 

 suppose that when several Echinococcus-colomes occur isolated 

 in an organ, the same number of the six-hooked embryos of the 

 Tcenia of the Echinococcus must have arrived at development. 

 Even Virchow has indicated, that all such colonies in one organ 

 may originate from a single embryo. In the appendix to the 

 second part of the German edition of my Text-book, I called 

 attention to this production by constriction or fission, which has 

 recently been pointed out by Luschka. The importance which 

 the mode of generation and life here mentioned possesses for pa- 



