CHONDRIOSOMES IN CELLS OF FISH-EMBRYOS 483 



poratioii within its substance, of other cell constituents, like 

 chondrioconts. 



With the recognition that zones of different consistence may 

 exist in a cell, the question of the structure of protoplasm is far 

 from being exhausted. My view of the problem is the foUow- 

 ng. Protoplasm appears to me to be composed essentially of 

 two substances, a ground-substance and the substance of the 

 chondriosomes. The ground-substance may show, as stated 

 above and emphasized by Conklin's experiments, zones of dif- 

 ferent density; one of these is the centrosphere. It may further- 

 more include within it fat or oil, yolk, etc., and, under special 

 experimental conditions, harbour some of the vital dyes. A 

 special structure may develop in the ground-substance, in con- 

 nection with the centrosphere, mainly during mitosis. Whether, 

 however, it has any other structure, such as a reticulum or an 

 alveolar system, as conceived by Butschli, seems to me to be ex- 

 tremely doubtful, notwithstanding the appearances in fixed 

 preparations. My opinion is based mainly on the movements of 

 the cell-constituents, and especially of the chondriosomes, — - 

 movements, the occurrence of which may be safely deduced from 

 the study of fixed preparations and which are demonstrated by 

 the direct observation of the living cell. I agree in this con- 

 nection with Lillie ('06), whose microsomes are, in part at least, 

 mitochondria, and with M. R. and W. H. Lewis ('15). One 

 might object that the movements described by these latter are 

 exaggerated by the special conditions to which the cells are sub- 

 jected in tissue-cultures; but it suffices that such movements are 

 possible. One should furthermore be reminded, in connection 

 with the question of the structure of the ground-substance, of A. 

 Fischer's experiments and of the criticism to w^hich Butschli's 

 alveolar theory has been submitted from the standpoint of 

 physico-chemistry, namely by Pauli ('02).^ 



•> From this, one will easily understand why I cannot consider as adequate the 

 term 'spongioplasm,' with which Conklin designates the more solid part of the 

 ground-substance. Concerning especially the comparison he makes between his 

 spongioplasm, and, on the other hand, Flemming's mitome and, to a certain ex- 

 tent, Boveri's archoplasm, I recall that it has been demonstrated that part of 

 Flemming's mitome (Meves, '10, 2) and Boveri's archoplasmic granules in the 

 egg of Ascaris (Meves, '14) are chondriosomes. 



