Artificial Parthenogenesis in Starfish Eggs 405 



areas; they also show that the nuclear membrane acts as a semi- 

 permeable membrane with reference to certain substances con- 

 tained wnthin it. The critical event, therefore, which conditions 

 this remarkable change in the properties of the cytoplasm is, 

 according to Delage, the passage of certain nuclear constituents {sue 

 nucleaire) into the cytoplasmic area {loc. ctt., p. 289). These 

 substances he suggests may either change the osmotic pressure 

 of the cytoplasm, or may influence the rate of oxidations, or may be 

 of the nature of particular electrolytes or enzymes. He was unable 

 to produce by artificial means any developmental changes in 

 such egg-fragments. 



The precise nature of the change induced in the egg-cytoplasm 

 in consequence of the dissolution of the germinal vesicle is as yet 

 unknown. The fact that the egg, if not fertilized within a few 

 hours, readily undergoes an oxidative change involving a coagula- 

 tion of the cytoplasmic colloids seems to point to an acceleration 

 of oxidations in that region — due possibly, as lately suggested 

 in an interesting paper by Mathews," to the liberation of oxidases 

 formerly confined to the nuclear area; if oxidases are of nuclear 

 origin, as certain facts seem to indicate,-^ such a consequence 

 v^ould naturally follow; the periodic dissolution of the nuclear 

 membrane in mitotic cell-division would thus have the significance 

 of providing for the distribution of the oxidases (synthesized in the 

 nucleus) throughout the cytoplasmic area; this would naturally 

 result in a periodic acceleration of oxidation processes in the cell. 

 Lyon-* has in fact shown that the production of carbon dioxide by 

 the dividing egg follows a rhythm parallel with that of the nuclear 

 division; and Loeb^^ has connected these oxidations with the syn- 

 thesis of nucleins from the compounds of the cell-protoplasm — 

 a process which is likewise characterized by a rhythm parallel with 

 that of the mitotic process. 



This general interpretation, though suggested by quite different 



^ Mathews: American Journal of Physiology, vol. xviii, p. 94, 1907. 



^ Cf . the references in my paper On the Oxidative Properties of the Cell-nucleus, in American 

 Journal of Physiology, vol. vii, p. 412, 1902. 



^ Lyon: American Journal of Physiology, vol. xi, p. 52, 1904. 



^ Loeb: Biochemische Zeitschrift, vol. i, p. 183, and vol. ii, p. 34, i()o6. 



