CLUSTER FORMATION OF SPERMATOZOA 137 



Lillie's theory becomes untenable, since this substance does not, 

 in all probability, originate from the egg but from the chorion and 

 since there is, as we have seen, no connection between the presence 

 of this substance and the power of the eggs of being fertilized. 



A second difficulty which Lillie has not considered lies in the fact 

 that the writer has shown that in addition to the membrane form- 

 ing substance still another, namely a corrective agency, is neces- 

 sary for the causation of the development of the egg. The cor- 

 tical change induces development but the egg as a rule perishes 

 if the second factor of artificial parthenogenesis is not applied 

 (hypertonic solution or lack of oxygen) . The writer is suspicious 

 that even a third factor may be implied. It is under these circum- 

 stances difficult to see how the assumption that the 'fertilizin' 

 causes development — leaving aside all other objections — can 

 act as an adequate substitute for the known facts of artificial 

 parthenogenesis. 



Lillie sees a proof for his idea in the statement of Glaser^ that 

 the filtrate from eggs of Arbacia ground up with an equal volume 

 of sea water will cause normal unfertilized eggs of the same species 

 to undergo one or more cell divisions if they are transferred from 

 the filtrate after one or two hours to normal sea water. Lillie 

 concludes from this that the egg contains its own fertilizing 

 substance, the 'fertilizin,' and that it was this ' fertilizin, ' liber- 

 ated from the eggs when they were ground up and contained in 

 the filtrate, which induced the cell division of the Arbacia eggs in 

 Glaser's experiments. Waiving the question of how this 'fertil- 

 izin' was 'activated' without the presence of sperm, the writer 

 sees no reason to assume that the egg extract acted through the 

 'fertilizin, ' or any other specific substance, since he has shown 

 that a large number of non-specific substances are able to induce 

 the first cell divisions (without membrane formation) in the egg 

 of Arbacia, e.g., traces of any weak base like HN3, or protamine.^ 

 A slight increase of osmotic pressure could also have such an 

 effect. It even suffices to let the eggs of certain females lie for 



* Science, N.S., vol. 38, no. 978, p. 446, 1913. 



^ Jour. Exp. Zool., vol. 13, p. 577, 1912; Arch. f. Entwcklngsmechn. d. Organ., 

 Bd. 38, p. 409, 1914. 



