114 
ME. EAIKEY OX THE STEUCTUEE AXE DEYELOP3IEXT OE THE 
the two kinds can be easily distinguished. See Plate X. figs. 6 h and G c. They are com- 
posed of a very highly refractive, dense, and perfectly homogeneous substance possessed 
of a slight degree of elasticity, and not acted upon by acetic acid. In the cun ed portion 
there is a ca\lty filled with a fibrous material, the other parts are perfectly solid. They 
are placed (see Plate X. fig. 5), like the radii of a circle, with the extremities of their 
handles turned towards its centre, which corresponds to the centre of the quadrangular 
area on which they are situated, and their handles not meeting at this point circumscribe 
a small circular space, which, if perforated, would correspond to the mouth of the ani- 
malcule ; but at this part there is no opening. The membrane is simply depressed, so 
as to present a conical hollow. By pressure upon the neck, this part can be made to 
protrude in the form of a tongue-like process. The handles of the booklets are connected 
with this process, so that when it moves they must move 'svith it. See Plate X. fig. 7 a. 
Besides the radiating fibres which connect the handles of the booklets to the membrane 
just described, there are other fibres which occupy the spaces between their ciuwed 
portions. These have an arched form with their concavity turned towards the booklets, 
into which they seem to be inserted. See Plate X. fig. 5 e. There are also two zones of 
circular fibres ; one is placed over the curved portion of the hooldets, and the other over 
their handles. Between these zones there is a circular inteiTal which contains the 
tubercles of the booklets. See Plate X. figs. 5 h and 5 c. These fibres lie close to the 
booklets, but in what manner they are attached to them, or whether they ai-e inserted 
into them or not, I am unable to determine. Although these fibres are sufilciently 
distinct in the well-developed Cysticercus to leave no doubt of their presence, yet their 
morphological characters are not sutficiently defined to indicate their precise nature. 
However, their connexion with organs which are ob\dously intended to perform a 
mechanical office, and which would be useless unless they admitted of a certain amomit 
of motion, furnishes a high degree of physiological e\idence, that if all these fibres ai'e 
not muscular, at least a part of them is. 
The Development of the Cysticercus cellulosse. 
The earliest indication of this species of Cysticercus, which admits of certain recogni- 
tion as a form of cystic entozoon, is the presence of a collection of reniform corpuscles 
of about a g^e g th of an inch in length and iw^th in breadth, mixed until veiy minute, 
highly refractive molecules of different sizes in the substance of a primaiy fasciculus of 
a muscular fibre, or between its sarcolemma and the sarcous elements. See Plate X. 
fig. 11. 
Though such a collection of corpuscles has a moderately definite shape, being some- 
what fusiform, yet it has not a complete investment. It soon, however, acquii'es a very 
distinct membranous covering, which is first apparent about its middle, and aftenvaixls 
at its extremities. Its dimensions in this stage of its formation may be about 
an inch in length and breadth, but these are by no means regular. The 
external investment at first appears only as a bright line of homogeneous substance, best 
