6O HARRIETT M. ALLYN. 



not be very different in the two cases. In the case of several 

 animals the same agents which will arouse a dormant seed will 

 arouse a dormant egg, that is, acids, bases, heat, increased 

 oxygen pressure, etc. The effect of these agents in a number of 

 seeds has been traced by Crocker and others, to the effect of the 

 agents in making the seed membranes more permeable to water 

 or to oxygen, according as the need might be. It would be going 

 too far to suggest that the egg is always dormant for the same 

 simple reason, an impermeability of its membrane to water or to 

 oxygen, but certainly some physical or chemical change is neces- 

 sary, which may be induced either by the sperm or by some non- 

 living physical or chemical agent, the problem being to find just 

 the need of the egg, that is, what is lacking to cause it to continue 

 its development. In the case of Ch&topterus one of the factors 

 lacking for differentiation would seem to be sufficient oxygen 

 or sufficiently high rate of oxidation. 



The question of the semi-permeability of the plasma-membrane 

 seems to be a very vital one. R. S. Lillie ('n), in his study of 

 artificial parthenogenesis in Arbacia, states that the critical 

 change in the egg to which the initiation of cleavage is due is a 

 well-marked and rapid increase of the permeability of the plasma- 

 membrane. He has lined up a number of salts whose power to 

 induce development runs parallel to their power to increase 

 membrane permeability. Among these salts are the chlorides, 

 bromides, and nitrates. The potassium salts of all of these, and 

 the sodium, calcium, and magnesium salt of the chloride, have 

 been found to induce development in Ch&topterus, and it seems 

 probable that they may exert the same sort of effect on this egg 

 that they do on Arbacia. Lillie ties up the change in permeability 

 with a change of electric polarization ('12), and a sudden diminu- 

 tion of the resistance to the progress of the oxidative energy- 

 yielding reaction, brought about by allowing the escape of the 

 products of oxidation, particularly carbon dioxide ('09). 



It is a well-known fact that developing eggs need much more 

 oxygen than resting, undeveloping ones. Various theories have 

 been brought up to account for this need. Loeb ('09) considers 

 that certain oxidative processes are advantageous in checking 

 the cytolysis set up in the initiation of development, which 



