DIRECT FORMATION OF DAUGHTER-BLADDERS. 623 



hijdatidosus would thus always be capable of producing brood-capsules 

 and heads as well as daughter-bladders. 



It is nevertheless equally certain, from the investigations of Helm, 

 which, being specially directed to this point, admit of no doubt that 

 there are hydatid Echinococci which are completely destitute of heads. x 

 In order to reconcile these forms with the above view, we must 

 suppose either that the worms had in the course of time lost the 

 capability of producing heads, or that the brood-capsules had become 

 daughter-bladders before the differentiation of the heads. 



The possibility of these processes cannot be denied, but Naunyn 

 has in the meantime proved that under some circumstances the 

 secondary hydatids originate directly, and independently of the other 

 products of proliferation. 



The process exhibited in this alternative mode of formation con- 

 sists essentially in the sacculation of the Uchinococcus-weill. This 

 begins by the collapse of the bladder after the partial loss of its fluid, 

 so that surfaces formerly opposite are here and there brought into 

 contact. When this contact, as often happens, leads to coalescence, 

 a portion of the parenchymal sheath separates like a fold from the 

 rest of the covering of the ^cAmococcws-bladder, and the portion of 

 the parenchyma thus separated forms the starting-point of the new 

 formation. First of all, it is changed by flattening and disappearance 

 of the internal cavity into a band, which in its turn generally breaks 

 up after a short time into a number of pieces. These become sur- 

 rounded by a system of concentric cuticular lamellae, and becoming 

 hollow inside, form so many new hydatids. The process bears the 

 greatest resemblance to the above - described exogenous budding, 

 except that when the hydatids grow out of the enveloping fold and 

 fall off, they do not make their way outwards, but into the bladder- 

 space. 2 



In some cases the process which we have described is only im- 

 perfect, and then there arise forms in which the inner surface of the 

 cuticle (as both Eschricht and I observed) is covered with cauliflower- 

 like excrescences, which always enclose hollow spaces. 



The two forms of Echinococcus which we have hitherto been con- 

 sidering, E. granulosus and E. Jiydatidosus, however different they may 

 be in other respects, agree at least in this, that they both form bladders 

 of considerable size. We know, for example, that they sometimes 



1 Loc cit.; regarding this point, see especially Observations iv., ix., andxi. 



2 Thus I was by no means wrong when I formerly sought, in the first edition of this 

 work, to derive the daughter-bladders of the Echinococcus hydatidosus from peripheral 

 buds, which essentially differ from the buds of the E. granulosus, only in reaching the 

 interior of the mother bladder by separation. I only erred in regarding this mode of 

 origin as the only one that ever occurs. 



