246 CYSTICERCOOIDS PARASITIC 



hyaline consistency (Fig. 6, b). This bladder still continues to 

 expand, adhering to the now fast-escaping head. The enveloping 

 membrane of the head has become contracted, and is drawn out 

 to a fine point (see Figs. 5 and 6), ultimately breaking away from 

 its point of attachment (Fig. 4) at the posterior end. This is the 

 rule, but there are exceptions (compare Figs. 5 — 7). The con- 

 tracting of this membrane has brought into view some very fine 

 muscular fibres, which, having broken away from the posterior 

 portion of the cyst-wall where they were attached, hang down 

 within the cyst in graceful, wavy threads. 



The outer membrane or ribbon-like appendage becomes disin- 

 tegrated under the influence of the re-agent, and finally becomes 

 absorbed if the process is prolonged. In the meantime the head 

 has been gradually progressing, the circlet of hooks slowly moving 

 upwards, until with a sudden jerk the contents of the cyst, con- 

 sisting of the head, suckers, rostrum, and hooks, are expelled, 

 together wdth the rudimentary-formed neck, and the observer has 

 before him on the stage of his microscope a perfect Tsenia-scolex 

 (see Fig. 7). A portion of the neck in this instance still remains 

 within the cyst, but there are times when the whole mass is freed 

 from the cyst. 



The head is spherical (see Fig. 8), and bears four suckers, a 

 rostrum, and a circlet of hooks. It is about three-hundredths of 

 an inch in diameter. In this instance the rostrum is inverted 

 (Fig. 7). In its natural position it appears as an elevation above 

 the head. The suckers are strong muscular swellings, yet they 

 are not such raised prominences as, for instance, in C arionis. 

 Their width is about the one-thousandth of an inch, and length 

 eight-hundredth of an inch, so that they are more oval than 

 spherical in shape. 



The circlet of hooks is situated below^ the dome of the 

 rostrum in a single circle, consisting of from twenty-two to twenty- 

 four hooks. The anterior root is broad, somewhat spatulate ; the 

 posterior root long and slender. The claw is slender, curved, and 

 terminates wnth a sharp point (Fig. 10). There is a marked 

 resemblance between this hook and that of Tcenia nana.^ Their 



* See Leuckart, " Parasites of Man," p. 658, Fig, 341. 



