386 Ralph S. Lillie 



tonic or hyperalkaline solutions is sufficient to produce normal 

 development.^^ Even without such after-treatment, eggs in which 

 membranes have been produced frequently cleave and under cer- 

 tain conditions may form blastulae; usually, however, such eggs 

 undergo breakdown or cytolysis within a few hours. Since this 

 change, as well as the cleavage, is dependent on the presence of 

 free oxygen, the inference is drawn that in some manner, possibly 

 by removal of anticatalytic substances, membrane-formation leads 

 to an acceleration of oxidation processes in the egg; these if 

 properly directed — as in consequence of normal or parthenogenetic 

 fertilization — lead to cell division and development; otherwise 

 they result in the destruction of the egg. Membrane-formation 

 has thus an important significance in development. 



My own observations on the starfish egg in some respects sup- 

 port this conclusion, though they can scarcely be said to do so 

 uniformly. That the process of membrane-formation is not essen- 

 tial to cleavage has been known for some time; Loeb's early studies 

 in artificial parthenogenesis supply instances of cleavage without 

 formation of fertilization membranes, and he cites other instances 

 in a later paper." It is also possible artificially to suppress mem- 

 brane-formation without destroying the possibility of cleavage in 

 the following manner: Eggs were placed 15 minutes after removal 

 in y/tit KCN solution in sea-water, and remained here 20 hours; 

 they were then washed in normal sea-water and warmed to '^^^'^ 

 for 70 seconds; these eggs formed no membranes although a con- 

 siderable proportion underwent irregular cleavage. On another 

 occasion the same suppression of membrane-formation without pre- 

 vention of cleavage was observed in eggs exposed to ^^W KCN for 

 only two hours. Although cleavage is thus to a certain degree 

 independent of membrane-formation, nevertheless normal cleavage 

 and development certainly do appear to be facihtated by the separa- 

 tion of the membrane. In the above cited experiments develop- 

 ment stopped short at an early stage, and I have never found eggs 

 to develop to an advanced stage under this form of treatment 

 without the formation of a membrane. On the other hand, when- 



'^ Loeb: loc. cit., also Archiv fiir die gesammte Physiologic, cxviii, pp. l8l and 572, 1907. 

 1^ Loeb: University of California Publications, Physiology, vol. ii, p. 153, 1905. 



