FERTILIZATION REACTION IN ARBACIA PUNCTULATA. 277 



tions of CuCl 2 required for cleavage-toxicity and that found by 

 v. Euler and Swanberg ('20) to be toxic to the action of saccha- 

 rase. McGuigan ('04), in an extensive set of tests of the effect 

 of the metallic salt solutions on the action of diastase, determined 

 the concentrations which inhibit its action for a series of metals. 

 Olsson ('21) also worked on the effects of the various salts of 

 silver and copper on the action of amylase, v. Euler and 

 Swanberg ('21 — II) found that the action on saccharase by 

 organic substances was not effected by the temperature. They 

 conclude that there is a binding of the enzyme through the 

 aldehyde group. McGuigan compares the action of the salts to 

 the solution tensions of their ions, though he finds certain irre- 

 gularities in the series. His results for diastase and those of 

 v. Euler and Swanberg for saccharase are in very close agreement. 



The data concerning membrane-inhibition in Arbacia do not 

 agree with the results noted by the above authors for enzyme- 

 poisoning. While chemical activity could explain the inhibition 

 effect satisfactorily, it would be difficult to conceive an immediate 

 correction of this, effect if the inhibiting factor were removed. 

 As has already been noted, when the eggs are removed to sea- 

 water from a solution in which inhibition is complete, if the 

 exposure has not been too long, there is an immediate recovery 

 and the eggs will produce membranes on insemination in the 

 normal manner. 



The present paper emphasizes the distinction to be made 

 between the initial events in fertilization as they are indicated 

 by the cortical activation, and the subsequent events which lead 

 to the period of cleavage. 



VI. Conclusions. 

 1. The chlorides of the following heavy metals inhibit mem- 

 brane formation in Arbacia in the following order and concen- 

 trations; — Au — iV/151,800, Cu — iV/42,030, Zn— iV/10,215, La — 

 iV/4,090, Al— N/1,780, Pt— iV/936, Pb— i^/554, Ni— iV/324, 

 Cd — iV/122.1, Co — iV/89.2. The effect of these concentrations 

 upon the cortical response of the egg is immediate. Eggs 

 inseminated 1 : 25 : 7.5 in these solutions immediately become 

 bombarded by many sperm, no one of which is able to activate 

 the cortex of the egg at the above concentration. 



