264 PHYSIOLOGY OF BACTERIA 



these necessities make the cell appear as a factory well 

 arranged after a carefully thought-out plan. This 

 definite arrangement is exhibited in the cells of higher 

 plants by the symmetry of the chromosomes in cell 

 division. Still, there must be considerable allowance for 

 individuality. 



There will be different degrees of complexity in the 

 different types of bacteria. A prototrophic bacterium 

 which builds its cells from CO2 and HNOsmust go through 

 more steps than a cell which uses sugar and amino acids. 

 The higher the claims of an organism are in respect to its 

 food, the simpler will be the growth apparatus, the less 

 will be the number of synthetic steps. 



We can imagine the food requirements to become so 

 highly specialized with certain parasites that the food 

 is almost identical with the protoplasm of the host. 

 The growth mechanism of these organisms would be 

 extremely simple. They would simply take part of the 

 host protoplasm, and incorporate it, after a few simple 

 changes, into their cells where it will be the parasite's 

 protoplasm. Such parasites could not have a cell wall; 

 it would prevent the direct ^^ intake" of such large 

 molecules. It would seem possible that these organisms 

 might consist of just one giant molecule. This might 

 fit the case of filterable viruses and bacteriophages 

 (Rahn, 19316). 



The knowledge of the filterable forms of well-known 

 bacteria is still too scanty to be included in this discus- 

 sion, but entirely new viewpoints are likely to be introduced 

 in our conception of the cell mechanism by these studies. 



(6) THE GROWTH PROCESS 



After having considered the probable arrangement of 

 the most essential molecules in the cell, we return to the 



