24 MORPHOLOGY 



substance and at the other gonidia are formed. When the 

 reproductive cells (gonidia) burst out of the sheath and are 

 thrown off, they usually are endowed with flagella temporarily 

 and swim about freely. In still an- 

 other group (Sphaerotilus or Clado- 

 thrix) there is developed what is 

 known as " false branching " as con- 

 trasted with the true branching of 

 a fungus or weed. The appearance 

 is due to the end cell of a filament 

 dividing twice. The second division 

 pushes to one side the product of the 

 first division, and each cell goes on 

 FiG.iS. Peniciliium glaucum. dividing separately, producing the 



Showing the true branching nii I>/T~" \ 



of a fungus of higher order. SO-Called "branch" (Fig. 15). 



After Fischer. Further description of the Tricho- 



bacteria will be given in connection with the chapter on 

 classification. 



Involution Forms and Pleomorphism. Among the bacilli, 

 some spirilla, and certain trichobacteria, there frequently 

 occurs protoplasmic degeneration and modification in form in 

 some species. This degeneration of the protoplasm within 

 the cell usually distorts the contour of the cell membrane, 

 producing what are known as " involution forms." This 

 degeneration occurs when the bacterial cell is not provided 

 with suitable food, is being subjected to temperature changes, 

 or to presence of a superabundance of excretory products. 



