96 STRUCTURE OF THE CYSTICERCUS CELLULOSE. 
cipal part of the Cysticercus thus far developed, and contained 
in the investment first described, are all of the same cha- 
racter, differing only in their form and size, according to their 
age and situation. Those situated about the centre, and 
forming the chief part of its bulk, are collected together into 
rounded masses, giving to many of the animalcules an ob- 
scurely annulose appearance. They are of an elliptical, or 
rather reniform figure. This form, however, is not essential 
to these cells, but merely results from the circular shape of the 
masses into which they enter, the convexity of each cell 
being a part of the outline of its respective mass. These cells 
contain minute granules, or rather molecules, which are va- 
riously disposed in different cells, so as to present a variety of 
appearances, such as circular spaces, which might be mis- 
taken for nuclei, but which seem rather to be produced by a 
deficiency of the cell’s contents at these parts, than by any 
distinct nucleus. The mode of formation of these cells must 
be examined in the growing parts of the animal, and for this 
purpose its extreme ends are best adapted. When one of 
these ends is about to have an addition made to its length, 
the investing membrane at this part becomes at first very 
thin, and then disappears. A clear space is next seen, 
having in some specimens the form of the part which is 
about to be added to the extremity of the entozoon ; in others, 
it has no defined limit. This space contains, in some cases, 
nothing but extremely minute molecules, of different shapes ; 
in others, these molecules are mixed with granules of various 
sizes, which have every appearance of having been produced 
by the coalescence of the molecules ; and lastly, with these 
molecules and granules, there are in other examples very dis- 
tinct globular cells, of a bright aspect, looking more like 
nuclei than perfect cells ; these soon become flattened oval, 
and ultimately take the elliptical form before described. All 
the time these changes are taking place in the molecules and 
cells, the membrane has been in progress of formation, so 
that when the molecules have disappeared, and their place 
has become occupied by perfect cells, the end of the animal 
is completed. The cilia are soon afterwards added. The 
lateral growth of these animats takes place in the same man- 
ner : the first indication is a separation of the cilia, which, it 
must be observed, are larger at the sides of an entozoon than 
at the extreme ends ; and then a thinning of the membrane 
supporting them ; and, lastly, the formation of globular cells, 
as before noticed. After the animals have become of a con- 
siderable size, and forced their way from the interior of the 
primary fasciculi into the cellular spaces between the larger 
