116 



I may anticipate so far as to say that I believe that these vessels 

 represent the water vascular system of the parent-cyst. 



A dark spot may be observed upon the surface of fig. 9. This 

 was a blunt yellowish wrinkled process, like that represented in the 

 lower portion of fig 7. It was the only projection of the kind in this 

 specimen. 



When such a sac as this is burst the Echinococci become everted, 

 and the secondary cyst turns itself inside out, so that the Echinococci 

 appear to be seated like Polypes upon a central stem. This curious 

 peculiarity has led to much misconception as to the mode of their 

 attachment within tiie cyst. Von Siebold, however, pointed out the 

 true nature of this process as far back as 1837* (vide infra). 



The smallest free secondary cysts varied in size, as I have said, 

 down to Y^th of an inch, when they contained only four Echinococci 

 (PI. XXIX. fig. 6). These, however, were quite as large as those in 

 the largest secondary cysts. 



The structure of the middle-sized and small vesicles was in most 

 respects the same as that of the large ones, but there was this differ- 

 ence, that they possessed, attached to their outer surface, by pedicles, 

 a variable number of oval boches of the same average size as the 

 Echinococci or less, but presenting a yellow wrinkled appearance, 

 containing very few corpuscles, often none, and either exhibiting no 

 trace of the circlet of hooks (fig. 6) or offering only a few, dark irre- 

 gular and -withered looking ones (fig. 7). It was impossible to con- 

 found these external bodies with accidentally everted internal heads, 

 three of which are represented at the upper part of fig. 7 ; the appear- 

 ance of the two being more markedly different than even the figure 

 represents it. 



I cannot help thinking that these withered Echinococci, for that, 

 as will be seen presently, is what they really are, are what Mr. Eras- 

 mus Wilson has figured as developing forms Qoc. cit.). 



Development. — We have found free Echinococci and free secondary 

 cysts contained in the fluid of the primary cyst : how do they come 

 there ? To answer this question we must return to the endocyst. I 

 found adherent to, and growing from it, a. fixed Echinococci, and 

 b. fixed secondary cysts. 



a. Fixed Echinococci. — These, in various stages of development, 

 are scattered all over the inner surface of the endocyst, as in the 

 diagrams E. and F. (PI. XXIX.) 



Elongated elevations of the endocyst (PI. XXVIII. fig. 5) are first 

 seen : within these the circlet of hooks and then the corpuscles make 

 their appearance : the elevation becomes a papilla, and the papilla, 

 gradually constricting itself at the base, becomes the oval Echinoeoc- 

 ciis, attached by a narrow pedicle. In this state the slightest touch 

 is sufficient to separate the pedicle from the endocyst, and then the 

 Echinococcus is set free. The pedicle contracts upon itself so as to 



* The Echinococci are figured in this everted state by Chemnitz (quoted by 

 Siebold, art. Parasiten,Vf agner's Encyclopaedia, &c.), by Erasmus Wilson (Medico- 

 Chir. Transactions, 1845), and by Busk (Microscopical Transactions, 1846). 



