342 THALLOPHYTES 
Many of the Bacteria are provided with cilia or terminal flagella, 
which enable them to move about independently. The cilia are 
distributed over the body in various ways and are extremely 
difficult to detect. Some of the motile forms are quite active 
and motility is one of the fea- 
tures suggesting that Bacteria 
are animals. Their cell walls 
are more or less slimy, and their 
protoplasm is not definitely or- 
ganized into nucleus and cyto- 
plasm. These features with 
their power of resistance suggest 
a relationship with the Blue- 
green Algae. They possess no 
chlorophyll and are almost ex- 
2 clusively parasites or sapro- 
s o—— C- eye 
a ee aon ne pies a phytes. The ability of the 
coceus form; a bacillus just below; protoplasm to endure extreme 
and a spirillum form at the bottom. cold, high temperatures, and 
At the left, above, a chain of bacilli; drying even surpasses that of 
ee ae oe eet td ore phe Blue-green Algae. Besides 
remaining separate or forming 
filaments, Bacteria commonly have another stage in which numer- 
ous individuals are held together in masses or colonies by a matrix 
of gelatinous substance formed from their walls. This stage 
is known as the zodgloea stage (Fig. 296). These colonies form 
the characteristic pellicles on nutrient media, as on the water in 
-which hay, Beans, Peas, or other organic substances are decay- 
ing, and on bouillon and various solid media (Fig. 297). When 
food is scarce or other conditions unfavorable, some forms shrink 
their protoplasm and enclose it in an inner heavy wall, thus form- 
ing what is called a spore. Enclosed in this heavy wall, they are 
inactive and extremely resistant to cold, heat, and drying. When 
transferred by wind or other agents to a suitable medium, they 
shed the heavy wall and become active again. 
Their method of getting food is essentially the same as in the 
Myxomycetes. Since they live on or within the food supply, 
they are in direct contact with the food material, and have only 
to change it to a soluble form and absorb it through their walls. 
They secrete enzymes which change insoluble foods to soluble 
