176 CARL RICHARD "MOORE. 



exposure of eggs to artificial agents has as a result, the imitation 

 of the effect of a spermatozoon in that full membranes are produced 

 around the egg, or when activation of fertilizin has been completed, 

 superposition of fertilization is impossible. If the activation has 

 been completed all fertilizin has been rendered inactive and a 

 spermatozoon has no effect upon the condition of the egg leading 

 to further development. 



The spermatozoon, it seems, to be able to produce its normal 

 effect, must enter into the developmental reactions at the be- 

 ginning. Whether some substance from the sperm forms a union 

 with fertilizin, that paves the way for a normal reaction, is as 

 yet problematical, but it is evident from these experiments and 

 others that sperm must enter the egg in the normal way if it is 

 to be normally effective. 



Thus fertilization appears very decidedly, to be a continuous 

 process each step leading to the next. If the first steps are 

 artificially initiated, spermatozoa entering, either do not become 

 effective at all or in doing so normal processes deviate so decidedly 

 from their natural course that developmental results usually 

 depart very decidedly from the normal. If the first steps leading 

 to fixation of fertilizin are artificially initiated and completed, 

 insemination, even if the spermatozoon penetrates the egg, has 

 no effect. If these first steps are incomplete and some fertilizin 

 remains unbound, partial fertilization may result in all degrees, 

 as evidenced by the abnormal course of cleavage and develop- 

 ment. 



VII. SUMMARY. 



1. Normal Arbacia eggs exposed to butyric acid (50 c.c. sea 

 water + 2.8 c.c. N/io butyric acid) and subsequently fertilized, 

 reveal a curve of fertilization falling from the normal reaction to 

 the optimum exposure to butyric acid for membrane production : 

 rising from the optimum exposure (20 sec.) to an over-exposure 

 of 2^-3 minutes; and again falling off until no further fertiliza- 

 tion is possible about 10 minutes. 



2. Eggs having been exposed for the optimum time to butyric 

 acid, have acquired an unfertilizable condition. If the mem- 

 branes are completely removed, sperm enter the eggs but do not 

 lead to development. The eggs, though sperm have entered 

 them, are not fertilized. 



