1 2 GENERAL MORPHOL OGY AND BIOL OGY. 



of their being spores is lacking. Their development has 

 been attributed by some to a process common in many 

 animal and vegetable cells, and known as plasmolysis. To 

 speak generally, when a mass of protoplasm surrounded by 

 a fairly firm envelope of a colloidal nature is placed in a 

 solution containing salts in greater concentration than that 

 in which it has previously been living, then by a process of 

 osmosis the water held in the protoplasm passes out 

 through the membrane, and, the protoplasm retracting from 

 the latter, the appearance of vacuolation is presented. 

 Now in making a dried film for the microscopic examina- 

 tion of bacteria the conditions necessary for the occurrence 

 of this process may be produced, and the appearances of 

 vacuolation and of polkorner may thus be brought about. 

 Plasmolysis in bacteria has recently been pretty extensively 

 investigated, 1 and has been found to occur in some species 

 more readily than in others. We may, however, conclude 

 that such appearances as vacuolation of the bacterial 

 protoplasm and polkorner are either signs of degeneration, 

 like the metachromatic granules, or are artificially produced. 

 All of them are most frequently observed in old or other- 

 wise enfeebled cultures. 



Biitschli has published interesting observations on the minute struc- 

 ture of some large sulphur-containing bacteria. These were found to 

 consist of an outer membrane enclosing the protoplasm, which was 

 divided into two parts an outer protoplasmic network containing bac- 

 terio-purpurin, and an inner part, the greater part of the latter being 

 stained blue with hoematoxylin, more deeply than the outer, in specimens 

 out of which the bacterio-purpurin had been dissolved. In this central 

 part thus stained there were red granules, which Biitschli regards as 

 the metachromatic granules of Ernst. The bacilli in the specimens he 

 examined seem, however, to have been healthy. Biitschli looks upon 

 the outer part of the central body as corresponding to the protoplasm 

 of an ordinary cell, the inner part as corresponding to the nucleus. 

 In one smaller bacterium he found evidence of the former only at the 

 end of the cell. He therefore thinks that the greater part of the 

 bacterial cell may correspond to a nucleus, and that this is surrounded 

 by a thin layer of protoplasm, which in the smaller bacteria probably 



1 Consult Fischer, " Untersuchungen liber Bakterien," Berlin, 1894; 

 " Ueber den Bau der Cyanophyceen und Bakterien," Jena, 1897. 



