Ui Dr. J. M. Hobson on 



capable of more or less gelatinous swelling so as to bind the cells 

 into a more or less compact mass. There are three types of form 

 as I have already indicated, namely, the cylinder, the spiral, and 

 the sphere, with certain modifications, giving origin to the terms, 

 which are used generically, of bacillus or a little rod, spirillum, 

 and coccus, the latter having generally the prefix micro — micro- 

 coccus. In spirillum a single cell forms only a portion of one com- 

 plete turn of the thread. With few exceptions the cells are very 

 minute, 25-500 ^^^^^ being about the most usual diameter. In 

 studying the morphology of fungi and algae, we are in the habit 

 of regarding the cells as only parts of the fabric, but in the case 

 of the Schizomycetes the cells appear to have more individual 

 importance. The reason for this is that the genetic connection 

 of the cells is of the loosest character, and there is, properly 

 speaking, no structure at all. Under the microscope the cells 

 commonly appear as mere crowds, no cell having any continuity 

 with its neighbour, or at most they are strung together like rows 

 of beads. Yet there are characteristic wiac?-oscopic appearances 

 whereby such differentiation as may be made out by the micro- 

 scope can be amplified. Another aid to differentiation is in 

 their life -products and effects. The term zooglcea is applied 

 to these aggregations of cells under certain circumstances ; but 

 since cultivation on solid media has largely replaced the older 

 methods of growing in fluids, the term has not the same signi- 

 ficance. 



Motility. — The cells may be non-motile throughout, or like 

 the hay bacillus (B. subtilis), they may be motile in the earlier 

 stages of their existence and non-motile in their later zoogloea 

 stage. In several cases cilia can be demonstrated. They ap- 

 pear in photographs, and the extraordinary development there 

 shown may even suggest a doubt of their real existence as 

 such, seeming " too good to be true." Micrococci are, as a 

 rule, non-motile, though a micrococcus has been figured with a 

 flagellum. 



.Reproduction. — This may be in the way of fission already 

 indicated, or by spore formation. In the former a fine transverse 

 line makes its appearance across the shorter diameter of the cell, 

 when there is a shorter one, dividing it into two equal parts, 

 which gradually thickens, being a development of cellulose, and 

 thus prepares for the complete separation of the cells. Spore for- 

 mation is most often endogenous, but some species are arthro- 

 sporous. In some species the spore, instead of forming in the 

 middle of the mother-cell, forms at one end, causing thereby a 

 drumstick appearance. In hay bacillus, anthrax bacillus, and 

 others, the spore formation begins only when the food material 

 is nearly exhausted, or the vegetative process is stopped through 

 certain products formed, and requires the presence of a free supply 



