INITIATION OF DEVELOPMENT IN EGG OF ARBACIA. 385 



that this double treatment of the eggs of sea-urchins produces top- 

 swimming larvfe. 



Loeb's work with agents of superficial cytolysis and the cor- 

 rective factor led him to solve the fertilization problem in this 

 wise: The sperm carries a lysin which initiates a superficial 

 cytolysis of the egg; thus the first effect of the sperm is com- 

 parable to the action of butyric acid. But the sperm, reasons 

 Loeb, also carries a corrective factor which checks the action of 

 the lysin that otherwise would kill the egg. This reasoning is 

 aided by the fact that in many ova the internal changes of ferti- 

 lization leading to cell division are preceded by demonstrable corti- 

 cal changes. 



I have attempted to point out that this theory of Loeb fails to 

 explain fertilization, and this for several reasons. Waiving not 

 only the fact that Loeb has produced cell division and swimming 

 plutei from uninseminated urchin eggs with the use of hypertonic 

 sea-water before or after the treatment with butyric acid, whereas 

 in the fertilization of these eggs the cortical changes always pre- 

 cede the internal cell division phenomena, but waiving also the 

 fact that hypertonic sea-water alone will give cleavage and plutei, 

 we must discard the superficial cytolysis-corrective factor theory 

 of fertilization for two reasons : First, this theory emphasizes too 

 much purely hypothetical substances in the sperm for which we 

 have not a single bit of evidence ; and, secondly, it wholly ignores 

 the fact that the egg is a highly irritable system, thus in no wise 

 different from other living substance ; that there are naturally 

 parthenogenetic eggs would indicate this. Moreover, the high 

 degree of susceptibility to shaking of such eggs as those of 

 Asterias, Am-phitritc, Nereis, and the effect of sea-water in starting 

 up maturation in eggs of Podarkc, Chcctopterus, etc., show how 

 labile are some uninseminated marine ova. This work on the 

 experimental production of cell division and larvae is of importance 

 in showing that ova are independent, activable systems ; they are 

 inherently irritable not a difficult physiological conception. But 

 as a means of elucidating the problem of fertilization, this work 

 on " artificial parthenogenesis," so called, has failed ; it has actually 

 obscured the fertilization problem. 



