278 CARL R. MOORE. 



chemical state of the egg has been brought about as a result of 

 the hypertonic treatment and fertilization is impossible. Of 

 what this change consists we do not know, but it is at least ac- 

 companied by an increased permeability of the egg and loss of 

 substances from it. Whether a specific substance necessary 

 for fertilization has diffused from the egg or whether it has 

 undergone new chemical combinations that have rendered it 

 unavailable and whether it may be the substance called fertilizin 

 are questions that cannot now be answered. But it seems sig- 

 nificant that here as in all previously modified conditions there 

 has always been a substance escaping from the egg into the 

 surrounding sea-water that could be detected by its sperm ag- 

 glutinating properties, if the eggs were still capable of fertiliza- 

 tion. That this unfertilizable condition is due to a new physi- 

 ological state of the egg itself and not to a physical condition of 

 the surface of the egg that might prevent sperm entrance, is 

 made certain by observation on preserved material. Sperm do 

 penetrate these eggs and sometimes produce weak changes 

 similar to fertilization or they remain entirely ineffective, de- 

 pending upon the condition of the egg itself. 



3. Conclusions of Section III. 



The results of this series of experiments seem to indicate that 

 a certain optimum exposure of the eggs of Arbacia to hypertonic 

 sea-water initiates changes within the egg that result in develop- 

 ment. That all do not segment is because the optimum exposure 

 for one egg is not the optimum for all. 1 Some have been over- 

 exposed, some under-exposed, but if the exposure was the 

 optimum one, swimming larvae were produced ; if less or greater 

 than the optimum perhaps only one or two cleavages resulted 

 and development ceased; if decidedly over-exposed or under- 

 exposed, cleavage does not occur. This quantitative relation 

 is then interesting from the standpoint of fertilization. If the 

 eggs were not perceptibly affected by the exposure they could be 

 fertilized; if the reactions initiated by the exposure were of 

 sufficient intensity to disturb the physico-chemical condition of 



1 The difference may be due to the factor of aging as Goldfarb ('16) has applied 

 the term. 



