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slight collar which almost invariably projects somewhat towards the 
outside (Fig. 1, A, B), more rarely towards the inside (Fig. 1, C). 
The envelope appears to be of the nature of cellulose, since it swells 
and takes on a violet colouration with chlor-zinc-iodide. 
The actual individual within the envelope has an apparently 
rigid periplast exhibiting a distinct spirally twisted striation which 
gives the protoplast a more or less crenate or minutely dentate 
Fig. 1. Isococcus sphagnicolus n. gen. et sp. A, B, C, ordinary individuals 
(B and C after staining with Iodine) showing the cilial apertures, the spirally 
striated periplast, nucleus, eye spot, and (in c) the pyrenoid-like bodies. D and 
G, oblique views of the front end, showing the cilial apertures and (in G) the 
aperture in the chloroplast through which the central nucleus is visible. E, 
small part of the anterior end of the envelope, much magnified to show the 
cilial collars and the small beak-like protrusion between them. F, individual 
with granular matter between periplast and envelope, also showing the 
pyrenoid-like bodies in the cell-contents. H-J, stages in division. In H the 
cilial apertures are still plainly visible, in I four almost mature daughter- 
individuals are seen, a, aperture in chloroplast; c, cilial apertures ; n, nucleus ; 
p, pyrenoid-like bodies; s, eye-spot. (A, H-J x 700; B, C, F x 950; D and 
G x 1500 ; E x about 2000). 
outline in optical section, whether viewed in the transverse or the 
antero-posterior plane (Fig. 1, A-D, G). Mention has already been 
made above of the colourless protoplasmic beak at the anterior end 
giving origin to the two cilia. The latter are rather more than 
twice the length of the whole individual and are relatively coarse, 
being easily seen in the living organism without the application of 
stains, The two cilia are identical as regards direction and mode 
