FERTILIZATION REACTION IN ECHINODERM EGGS. 2J3 



In some cases membrane elevation could not be induced by arti- 

 ficial agents in these stale eggs. In such cases the egg bursts 

 through the membrane, forming either a number of vesicles or 

 erupts after the manner of an extra-ovate. This further indicates 

 that the agents used have an expansive effect upon the egg con- 

 tents as well as on the membrane. When extra-ovates are formed 

 from stale eggs by these agents the vitelline membrane separates 

 from the egg contents. As .this is not the case when extra-ovates 

 are induced in fresh eggs, one may again conclude that the vitel- 

 line membrane loses its elasticity and distensibility on standing. 

 The membrane appears much stiffer and firmer than in fresh 

 eggs; in all probability it is coagulated. 



7. Conclusion. In conclusion I may be permitted to reiterate 

 an old view that the activation of the egg by the sperm is of the 

 nature of a stimulation or excitation. Among the characteristics 

 of a stimulation are: (a) many different agents are capable of 

 exciting the same effect in the protoplasm which is stimulated 

 so that there is no specific relation between the properties of the 

 agents and the change invoked in the protoplasm ; (&) the changes 

 induced in the protoplasm stimulated are altogether in excess of 

 the energy t content of the stimulus; (c) the changes invoked in 

 the stimulated protoplasm depend upon the constitution of the 

 protoplasm and not upon the nature of the stimulus; d) the 

 excitation is transmitted from the point of application of the 

 stimulus. It is evident that the activation of the egg exhibits 

 these characteristics. Many different agents are able to induce 

 activation. There appears to be no specific relation between the 

 changes induced in the egg and the physical and chemical proper- 

 ties of the stimulating agents. To suppose that the sperm brings 

 into the egg some substance which evokes the activation changes 

 is I think just as far from the truth as to suppose that the various 

 agents which induce a nerve impulse do so by injecting some 

 substance into the nerve. I think one must agree fully with 

 Lillie ('19, Chap. VII) that the egg is "an independently activ- 

 able system" and "possesses all of the substances necessary for 

 activation." Finally it has been shown in at least a number of 

 cases that the fertilization reaction is initiated at the point of 

 sperm entry and is transmitted from this place over the egg. The 



