166 PROBLEMS OF FERTILIZATION 



butyric acid is a very favorable strength for artificial 

 activation; it was therefore used constantly in these 

 experiments. Now it must be emphasized that there 

 is no visible change in the eggs while in the butyric 

 acid; but when the eggs are transferred to sea-water, 

 if the time of exposure has been right, the eggs form 

 membranes as they do after insemination, and sub- 

 sequent treatment with hypertonic sea-water will cause 

 them to develop normally. By varying the time of 

 exposure to the butyric acid we get varying degrees of 

 activation as expressed in membrane formation by the 

 eggs and in their capacity for development; this pro- 

 ceeds up to an optimum. If the exposure to butyric 

 acid be prolonged beyond the optimum the capacity for 

 development gradually falls off to zero. 



It is clear that butyric acid produces a condition of 

 pre-activation in which the egg activates when returned 

 to its normal environment; but if the treatment be too 

 short the pre-activation is insufficient; if it be too long 

 some other condition arises that inhibits normal acti- 

 vation. 



If, then, insemination is practiced on these eggs 

 after their return to sea- water, it is found to be success- 

 ful in inverse proportion to the degree of activation 

 induced in the sea-water up to the optimum point, at 

 which superimposed insemination has no effect. Be- 

 yond this the curve of superimposed fertilization shows 

 a second rise and fall to zero. At the optimum point 

 for artificial activation, at which all eggs form mem- 

 branes and are capable of development after treatment 

 by hypertonic sea-water, the sperm has absolutely no 

 fertilizing effect on the eggs, whatever its concentra- 



