PLASTJDS AND CHONDRIOSOMES 123 



The existence of such a genetic relationship between chondriosomes 

 and plastids as that described above has been denied by many writers, 

 among whom may be mentioned Lundegardh (1910), Meyer (1911), 

 Rudolph (1912), Lowschin (1913, 1914), Scherrer (1914), Miss Beckwith 

 (1914), Derschau (1914), von Winiwarter (1914), Sa'pehin (1915), 

 Chambers (1915), M. and W. Lewis (1915), and Harper (1919). These 

 workers for the most part hold that chondriosomes are not distinct cell 

 organs at all, but regard them rather as more or less transient visible 

 products of protoplasmic activity. Derschau asserts that they arise 

 neither de novo nor by fission, but that they are merely small masses 

 of plastin and nuclein concerned in nutrition, arising from basichromatin 

 at the surface of the nucleus. Miss Beckwith speaks of them as differ- 

 entiation products of the cytoplasm. Lowschin, who made some ex- 

 periments in the production of artificial chondriosomes, believes them 

 to be due to the emulsified state of the protoplasm and in some instances 

 to the action of fixing agents upon it. To Chambers they appear in 

 living cells not as persistent structures but as temporary physical states 

 of the colloidal substances composing protoplasm. M. and W. Lewis 

 have studied them in tissue cultures and observe that they are continually 

 being formed and used up, and that they show no sharply distinct types. 

 Faure-Fremiet (1910a) distinguishes "mitochondria," which have an 

 individuality of their own and are permanent cell organs, from "lipo- 

 somes," which are temporary accumulations of reserve substance. 



The almost universal occurrence of chondriosomes in the cells of 

 living organisms, and their frequent alterations in number and appear- 

 ance, suggest a connection with some fundamental process going on 

 almost constantly and common to all living matter. That this process 

 may be oxidation, the chondriosomes being a "structural expression of 

 the reducing substances concerned in cellular respiration" (Kingsbury), 

 has been regarded as highly probable by Kingsbury (1912), Mayer, 

 Rathery, and Schaeffer (1914), N. H. Cowdry (1917, 1918), and others. 

 Evidence favoring this interpretation is seen in the fact that the chondrio- 

 somes occur so widely in the cytoplasm, which acts as a reducing sub- 

 stance; and also in the close similarity between their chemical composition 

 and that of phosphatids, which appear to be capable of auto-oxidation. 



Conclusion. From the foregoing review it should be more than plain 

 that the state of our knowledge of chondriosomes is such that almost no 

 definite final statements can be made regarding their origin and function. 

 The evidence at hand apparently indicates that the class of cell inclusions 

 known as chondriosomes comprises a variety of bodies which play differ- 

 ent roles in the life of the cell. It is scarcely open to doubt that some of 

 them are temporary accumulations of substances involved in metabolism, 

 appearing and disappearing in the cell in a manner somewhat analogous 

 to that of starch. The most plausible hypothesis concerning the specific 



