348 



Dr. D. Ellis. 



[May 17, 



the cytoplasm a light transparent brown, whilst the sheath remains 

 uncoloured. Methylene-blue, or carbol-fuchsin, or Bismarck -brown may also 

 be used for staining, but iodine is undoubtedly the best. In young cells 

 the cytoplasm is unvacuolated, and in it are usually found some strongly 

 refractive round bodies. These are oil-bodies and have already been 

 noticed by Biisgen (2). In artificial cultures the oil-drops are wanting and 

 in their place we find large empty spaces in the cytoplasm. Hoeflich (12), 

 who worked with artificial cultures, does not mention them, but states that 

 the cytoplasm is strongly vacuolated, hence we may conclude that in 

 artificial cultures the conditions are not favourable enough to enable the 

 organism to store food material. For their observation I have taken 

 samples direct from nature, and examined as soon as possible after collection. 

 This is necessary because the threads decompose very rapidly. A cell may 

 have two or three large oil globules or a larger number of small ones 

 (fig. 11, b). In many cells I also found glycogen as a reserve material, either 

 with or without oil-globules (figs. 12, 13). This reserve material was 

 sometimes found as a covering to the oil. 



I am strongly of the opinion that the membrane is often used as a depository 

 for reserve food material. This is shown by the fact that, when there was 

 much glycogen in the cell, the colour of the membrane when stained with 

 iodine could not be distinguished from that of the glycogen deposited in 

 the cytoplasm. On the other hand, the membranes of cells belonging to 

 threads of a five to six days' old culture, in which glycogen was never 

 found, were markedly free of colour when treated with iodine. It must 

 be borne in mind that the membranes of bacteria and their allies have not 

 the same firm consistency as have those of the higher plants. They are 

 more readily permeable, and solid substances enclosed in the cell can 

 sometimes be seen being thrown out without any apparent difficulty when, 

 during staining, the absorption of certain liquids sets up a high osmotic 

 pressure. In the case of Spirillum volutans I have on several occasions 

 observed the ejection of volutin granules during the process of staining. 

 Such membranes are probably well adapted to serve as depositories of food 

 material, and it is a membrane of this kind that Cladothrix possesses. 



Some interesting facts are brought to light by the observation of threads 

 that are gradually undergoing decomposition. Large gaps are seen in the 

 cytoplasm, marking the spots originally occupied by the reserve food 

 material ; the membrane, being more resistant, stands out clearly in such 

 cells, thus giving us perhaps the best evidence of the morphological unity 

 of this organ (fig. 15). In still older threads the individuality of the 

 cells is lost, and finally the whole breaks down, when irregular lumps of 



