STRUCTURE OF BACTERIA 117 



very limited extent, make their appearance as small processes or 

 lobes on the surface. As the result of maltreatment, on the 

 other hand, whether from pressure or from the action of chemical 

 substances, there develops, as a rule, a layer of protoplasm of 

 this kind over the whole surface, which gradually disappears 

 again when these influences cease. 



A clear border below the limiting contour of the surface is 

 always very plainly noticeable even with lower powers ; on the 

 other hand, I have not succeeded as yet in observing with 

 certainty any radial striation of this border, which in other 

 respects possesses all the characters of an alveolar layer. In the 

 rest of the protoplasm also I was not able to recognise distinctly 

 a fine alveolar structure during life ; the well-known coarsely 

 frothy structure of the protoplasm of Pelomyxa cannot, of course, 

 be placed on a level with the minute foam-like structure. If, 

 however, small and rather compressed individuals be rapidly fixed 

 with picro-sulphuric-osmic acid under the cover-slip, the entire 

 protoplasm shows the finely honeycombed structure especially well, 

 and the alveolar layer usually shows up on the surface with a 

 distinctness and sharpness such as I have hardly seen elsewhere. 

 The radiate layer is shown just as beautifully round the numerous 

 nuclei. Also in the hyaline, and in any case very fluid proto- 

 plasm, which under the above-mentioned circumstances makes 

 its appearance at the surface, the radiate layer of alveoli and 

 the honeycombed structure can be made out excellently after 

 fixation. 



The protoplasm of Pelomyxa possesses an especial tendency 

 to break up into a great number of spherical drops before its 

 final death. Each of these drops shows a beautiful layer of 

 radiate alveoli at the margin after fixation. 



2. On Protoplasmic Structures in the Pacteria and 

 allied Organisms 



In a work which appeared in the commencement of the 

 year 1890, I tried to show that Bacteria and Cyanophyceoe 

 possess essentially the same structure, and that in both there 

 could be demonstrated a nucleus of considerable size and 

 with a beautiful alveolar structure, which at least in the 

 larger forms of Bacteria, and universally in the Cyano- 

 phycece, was surrounded by a thin layer of protoplasm 

 of alveolar structure. I would have contented myself with 

 simply referring here to that work as a proof that these 



