170 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
(F) Size. The size varies between 4/* and 8^ in diameter. In certain 
cultures there are specimens larger than this (circa iom) ; such forms occur in old 
cultures and in cultures which are degenerate and showing no tendency to develop. 
Many of these large forms are ruptured, and are in reality but empty capsules. 
The maximum and minimum diameters given, 4/* and represent the limits 
of the size of the type in healthy recent cultures. 
(7) Structure. There are two chief varieties of type A present in all cultures in 
varying proportions. 
The following descriptions are of cultures all stained with methylene blue* 
(Plate XIII, Figs. 1 and 2) : — 
Variety 1. The organism possesses a capsule which is very delicate in most 
specimens, but in older cultures it is denser and possesses a double contour. Within 
this is a delicate cell network and nucleus, both of which are with difficulty made 
out. The whole cell either remains colourless or takes a diffuse pale rose colour, 
and neither cell network nor nucleus are chromatophylous. 
In the majority of specimens are one or more highly refractile granules. They 
usually take no stain, but occasionally take a dense blue. 
These granules in young cells are scattered in different parts of the interior, 
but in other cells are collected into a spherical or oval mass, situated in the centre or 
slightly eccentrically. 
In these cells, with central mass of granules, no cell network outside this mass 
can be seen, nor a nucleus distinct from it. Vacuoles are seen in many of the cells, 
especially in older cultures ; occasionally these contain a refractile granule, either 
motionless or exhibiting active 'dancing' movements. 
Variety 1. This variety shews a definite capsule of varying density. Within 
this is a mass of finely granular protoplasm which takes an intense blue colour. This 
intensely coloured protoplasm may either completely fill the interior of the cell or 
may present itself as a spherical mass, with an uncoloured ring of apparently structure- 
less protoplasm between it and the capsule. At or about the centre of this granular 
chromatophylous protoplasm a nucleus can be distinguished. 
As already stated, both these varieties are to be seen in all cultures. 
In young glucose agar cultures variety 1 is almost exclusively seen, specimens 
of variety 2 are few in number. In young glucose broth cultures the two varieties occur 
about equally in number. In glucose broth cultures, four days old and onward, variety 2 
is the more common ; in such cultures there is always a sediment, and in this sedi- 
ment growth variety 2 predominates to a greater extent than in the suspended part 
of the culture. 
If dried coverslip preparations of the organism are made and stained, certain 
peculiar appearances are obtained. In the process of drying, the organisms 
* Methylene Blue, 4 grms., Soil. Bicarb., 2 grms., Water, 400 c.c. 
