FERTILIZATION AFTER INITIATION OF DEVELOPMENT. 293 



which union curtails any further possibility of a subsequent 

 fertilization. If the same conditions are produced by artificial 

 parthenogenesis the same lack of the capacity for fertilization 

 is evident. 



Whether the lack of this capacity is due to the absence of one 

 substance or of several substances, and whether the substance 

 called fertilizin is the essential one or is only an indication of a 

 certain physiological state of the egg is unknown. But in every 

 case, so far examined, fertilizin has been present if the eggs could 

 be fertilized and has been absent if there was no capacity for 

 fertilization. 



These results are weighty argument, if not definite proofs, 

 against any idea of a sperm-borne substance that is necessary 

 for the initiation of and the continuation of development. 

 There is no evidence that the spermatozoon imparts a "lysin- 

 like" substance that produces cytolysis within the egg and 

 later carries into the egg a "corrective agent" to check the 

 imposed cytolysis. The egg possesses all the substances it needs 



for development. 



VI. SUMMARY. 



1. If Arbacia eggs are exposed to a weaker and a stronger 

 concentration of sea-water for varying lengths of time a per- 

 ceptible gradient of effectiveness from the entire absence of any 

 reaction to an essentially normal parthenogenetic reaction is 

 apparent. 



2. The effective exposure is accompanied by a perceptible 

 condition of increased permeability and substances escape from 

 the eggs. 



3. The superposition of insemination on the optimum hyper- 

 tonic treatment does not increase the percentage of development. 



4. Eggs when exposed to hypertonic sea-water for two hours 

 usually cannot be fertilized; and in such a condition fertilizin 

 cannot be detected by any known method. . If however there 

 yet remains a certain capacity for fertilization, fertilizin can be 

 detected by its sperm agglutinating properties. 



5. If Arbacia eggs are exposed to activating agents the perme- 

 ability of the egg is increased, substances are lost from it and 

 fertilization is impossible. 



