288 



Another case of variability, similar to the loss of chemosynthesis by feeding 

 with organic substances, I observed in various lower Algae respecting photosyn- 

 thesis. For a long time I have been cultivating the gonidia of the lichen Xanlhorea 

 parietina, which are identical with the Protococcacee Cystococcus humicola. The first 

 isolation was made by streaking off the said lichen, rubbed to a mash, on pure 

 agar with salts and cultivating it in light. The thus obtained green, pure colonies, 

 develop very readily as well in the light as in the dark on maltextractagar 

 and form large green masses, which, however, in course of time completely lose 

 the power of photosynthesis, so that neither on agar with salts, nor in anorganic 

 liquid media any growth takes place. Microscopically no difference is to be seen 

 between the inactive chloroplasts of these cells and the active ones of normal 

 C\sto coccus cells. 



The very same I observed in cultures of Plenrococciis vnlgaris, isolated from 

 the bark of trees and long cultivated on maltextractgelatin, on which it grows 

 vigorously in the dark without losing the green colour. Hence it is clear that 

 for photosynthesis the presence of chlorophyll in the living protoplasm is not 

 sufficient, but the process requires still another factor, which may get lost through 

 cultivation with organic food. 



The greater part of the chlorella's of Hydra viridis, undoubtedly belonging 

 to the so easily cultivable species Chlorella vulgaris, lose, when out of the Hydia 

 body, howsoever fed, as well the power of photosynthesis as that of growth, so 

 that it is very difficult to cultivate them. So, here is a case where change of 

 food causes the loss as well of the function of photosynthesis as of that of growth. 



Conclusion. 



Some of the common denitrifying bacteria, such as B. denilrificans and B, stutzeri 

 (these names taken in a broad sense), and probably some other species, may 

 occur under two physiologically different modifications, which are hereditarily 

 constant, when their feeding conditions remain unchanged. One form, the autotropic, 

 is adapted to the anorganic medium (sulfur- or thiosulfate- chalk-nitrate) and 

 shows chemosynthesis; the other, the heterotrophic form, requires organic food. 

 They may be compared to the oligotrophic and the polytrophic condition of the 

 nitrate ferment. Intermediate forms, feebly denitrifying in the anorganic medium, 

 also occur, hence the autrotrophy may be lost gradually. 



The heterotrophic forms preserve the power of denitrification with organic food. 



The nitrite ferments of the ammonium salts are also related to hereditary 

 modifications with the character of saprophytes, living on organic food and unable 

 to oxidise ammonium salts. 



Great changes in the nature of the food may thus be the cause of hereditary 

 modifications of certain factors, and this seems to throw some light on the causes 

 which underlie ontogeny. 



