STUDY OF FERTILIZATION 429 



It seems likely, therefore, that a disturbance of the electrical 

 properties of the film will result in a loss in the stability of the 

 film. Such reactions are well known in the case of non-lipoid 

 films, e. g. in rhythmical catalysis (Bredig, 1), and in the activa- 

 tion of passive iron ^ (Lillie, 23). 



Before passing on to the later stages of fertilization in the 

 echinoderm or annelid egg, reference must be made to the 

 activation of the eggs of Amphibia. There are two methods of 

 artificial activation, (a) by mechanical puncture, (b) by electrical 

 stimulation. These facts seem to indicate most clearly that 

 the process is essentially physical in nature. In the first case 

 the egg is subjected to an injury current with an inevitable 

 wave of negativity sweeping over the egg-surface. In the second 

 case the electrical disturbance is set up precisely as in the 

 stimulation of a muscle or nerve. The only difference is that 

 no recovery process ensues. It seems almost impossible to 

 harmonize these facts with the theory of Loeb, or with that of 

 F. Lillie. 



The beautiful experiments of F. Lillie (20) enable us to be 

 quite sure that the changes induced in the echinoderm or 

 annelid egg by artificial ' membrane formation ' are precisely 

 those changes which are set up by contact of the egg with 

 a spermatozoon. Lillie showed that the cortical changes in 

 the egg of Nereis are completed on contact between the egg 

 and spermatozoon : if the latter be now removed by means 

 of the centrifuge, the eggs undergo a series of changes essen- 

 tially similar to eggs which have been activated by means of 

 artificial membrane-forming agents. Development of the egg 

 depends in each case on events which take place subsequent 

 to this phase. The whole process of normal fertilization 

 is divisible into two well-marked phases, (a) activation, due to 

 cortical changes produced by contact with the spermatozoon, 



' The activation of an egg and a piece of passive iron appear parallel 

 phenomena ; and in this respect the activation of echinoderm eggs by 

 means of metallic silver (Herbst, 13) may warrant further mvestigation, 

 although it is not clear whether the metal or one of its salts is the activating 

 element. 



NO. 263 H h 



