CYSTICEECTTS CELLULOSE, AS FOUND IN THE MUSCLES OF THE PIG. 119 
which are of various shapes, but still all have a contour more or less curvilinear, and 
the smaller ones are of a spherical figure. Their size varies from about that of the third 
part of a handle of a perfect booklet, to a particle so minute as scarcely to be appre- 
ciable by the highest powers of the microscope. There are all the intermediate sizes 
between these extremes. Notwithstanding, however, these extremes of size and form, 
all these particles possess the same optical and physical properties, so as to be perfectly 
recognizable, both when apart and when joined together in the perfect booklet. See 
Plate XI. figs. 10 and 12, in which they present no appreciable change in their general 
appearance. 
At a period of the development a little more advanced, some parts of a booklet can 
be recognized among these various forms, especially the curved portion, as being most 
characteristic ; also some parts of a handle can be distinguished ; lastly, the larger pieces, 
formed obviously by the coalescence of smaller ones, can be seen fused, as it were, 
together, more or less completely in a newly-formed booklet, in which frequently the 
joining is so incomplete as to amount to httle more than mere apposition of the coalescing 
particles. See Plate XI. figs. 12 and 14. 
The part first formed is the hook : this has at first its internal cavity rather larger 
than that in the older ones, and there is an irregularity of its outline, indicating a want 
of complete union of its component particles. The handle is formed next : this is more 
remarkable for its want of symmetry than the curved part, some pieces of it appearing to 
be merely apphed to each other. See Plate XI. figs. 10 and 14. Lastly, the tubercles are 
added. Neither the whole nor the parts of a booklet undergo any increase in size after 
being once formed, but, on the contrary, rather suffer a slight diminution. The booklets 
of the old Cysticercus are frequently smaller than those of the young ones. But these 
organs vary a little in different animalcules, being rather smaller in some than in others, 
but those belonging to the same individual are remarkably regular in this respect. 
From the facts that have just been mentioned, the booklets of the animalcule in ques- 
tion do not appear to be formed by cell-development. For by the most careful examina- 
tion of these organs, both recent, and after the application of acids, I have not been able 
to distinguish anything which can be looked upon as a cell or cell-nucleus, calculated to 
give the idea of theh being developed from previously existing cells, or in dependence of 
cells; but, on the contrary, all the various forms and characters which they present during 
the process of their formation simply indicate the coalescence of very minute spherules 
of an homogeneous material, exceeding the number of a complete set of booklets, into 
small globular masses, and these again into larger pieces, and so on successively, until 
recognizable portions of booklets come into view, which, coalescing, build up, as it were, 
an enthe organ. 
It is worthy of remark, that if these structures had been produced directly from the 
metamorphosis of previously existing cells, the circumstances connected with their for- 
mation would have been the most favourable for observing both the original cells and 
the changes which they passed through ; indeed, so much so, that it is almost impossible 
E 2 
