1 1 6 Marshall Ward . — On the Characters , or 
(/3) Sheathed forms. 
(i) Unbranched. 
Crenothrix . 
(ii) With false ramifications. 
Cladothrix. 
B. Colonial or aggregated forms. 
(a) Non-sheathed. 
(i) Micrococcus-like cells. 
Pundula. 
(ii) Rod-like cells. 
Polybacteria . 
(0) Sheathed. 
(i) Micrococcus-like cells. 
Ascococcus. 
(ii) Rod-like cells. 
Ascobacteria. 
(iii) With spiral segments. 
Myconosfoc. 
II. The planes of division run in two directions, and the membrane- 
like surfaces break up into groups of quadrates. 
Men's ia. 
III. There are three planes of division, resulting in the development 
of solid cuboidal masses. 
Sarcina. 
It may be regarded as an objection to Van Tieghem’s 
system that the three chief divisions are so very unequal, and 
that some of the characters employed for subdividing the first 
primary group, which contains nearly all the forms, are of 
more importance than those used for separating the three 
main divisions. This criticism seems well-founded if we 
remember that planes of division only affect the vegetative 
stages. Van Tieghem himself points out that the division- 
planes in the second and third groups do not always follow 
equally rapidly, and in their proper order : a young Merista 
may be uniseriate, and a young Sarcina meristate. 
It should be stated that Van Tieghem does not himself 
draw up a detailed table, possibly because he recognised how 
