NEW PERITRICHOUS INFUSORIAN, 243 
primary pocks. It is further to be noticed as a collateral 
fact that in consequence of the number and progressive dila- 
tation of the vesicles at the expense of the deepest layers of 
the rete, the inter-papillary processes become obliterated, so 
that the corium is marked off from the rete by a line which 
is almost as even as it is in sections of the natural skin. As 
a further result of the distinction of the vesicles, it is some- 
times seen that the deepest cells of the rete are altered in 
form by compression. As regards the distribution of the 
vesicles in the secondary pustule, it is to be noticed that even 
in those pocks that exhibited a marked central depression, 
the most numerous and well-developed vesicles were found 
towards the centre ; this is clearly inconsistent with the sup- 
position that the depression is caused by the disappearance 
of previously existing vesicles. 
As has been already stated, the vegetations contained in 
the lymphatics of the corium, as well as those occupying the 
vesicular cavities, presented the same characters as those 
which have been already described in the previous section. 
In some vesicles the mycelium is imbedded in a finely 
granular matrix, which is to be regarded as coagulated 
plasma; in others the matrix is almost homogeneous, and is 
stained slightly by carmine and hzematoxyline. The myce- 
lium itself, as well as the spores which devolve from it, 
exhibit a bright and shining appearance. Eventually the 
mycelium is transformed by a process of rapid fructification 
into a mass of micrococcus resembling zoogiza, the characters 
of which are not to be distinguished from those of the similar 
masses which are met with in the primary pustules when 
examined at a later stage of their development. 
On a New Peritrricnous Inrusortan (Cyclocheta spon- 
gille). By WM. Harcuetrr Jackson, B.A., F.LS., 
Demonstrator of Anatomy, University Museum, Oxford. 
With Plate XII. 
Tue Infusorian figured Pl. XII was originally found by 
my friend Mr. W. H. Poole, of Magdalen College, while en- 
gaged in examining a fine fresh-water sponge (Spongilla 
fluviatilis) taken from the river Cherwell. He was good 
enough to give me the first specimen as well as another 
he found subsequently. ‘These two, together with others 
