580 FRANK R. LILLIE 



and an ovophile combining group. The spermatozoon is rep- 

 resented with a receptor capable of fitting the spermophile 

 group of the fertilizin; the egg similarly contains receptors capable 

 of fitting the ovophile group of the fertilizin. Within the egg 

 represented as alternating with the egg-receptors, are also found 

 certain molecules (anti-fertilizin) capable of uniting with the 

 spermophile group of the fertilizin. 



Union of a sperm receptor with a spermophile group of the 

 fertilizin molecule activates the latter so that the ovophile group 

 forms a union with an egg-receptor (fig. 1, sector 2, a); and I 

 have postulated that the fertilizing action is the Result of this 

 union. But the activation of the fertilizin can by no means be 

 regarded as confined to those molecules bound by the single pen- 

 etrating spermatozoon. On the contrary, as we have seen that 

 all the spermatozoa used in insemination bind only a minute pro- 

 portion of the fertilizin contained in the eggs, it is necessary to 

 assume that the activation of the fertilizin spreads beyond the 

 point of attack of the successful spermatozoon ; this is represented 

 in figure 1, sector 2, h and c. Inasmuch as membrane formation 

 is practically instantaneous all around the cortex, the activation 

 of the fertihzin must spread with extreme rapidity; an activated 

 molecule of the fertilizin must transmit the activated condition 

 to its neighbor, in a fashion that may be compared by analogy 

 to the spread of a stimulus. The assumption here is no different 

 in principle from that which must be made in any theory of the 

 fertilizing effect of thfe spermatozoon, and therefore, no new diffi- 

 culty is introduced. 



The postulated mechanism admits of five blocks in the process 

 of fertilization viz.: 1. Absence of the fertilizin (fig. 1, sector 3); 

 2. Occupancy of the sperm receptors (fig. 1, sector 4); 3. Occu- 

 pancy of the egg receptors (fig. 1, sector 5); 4. Occupancy of the 

 ovophile side-chain of the fertilizin (fig. 1, sector 6) ; 5. Occupancy 

 of the spermophile side-chain (fig. 1, sector 2, h and c). Of these 

 we have examined and discussed in the body of this paper the 

 first, fourth, and fifth, the first in the case of the long washed eggs, 

 (p. 549) the fourth in the case of the inhibitor contained in the 

 blood (p. 563), and the fifth in the case of the non-fertilizable 



