386 E. E. JUST. 



For these two reasons, then, the superficial cytolysis-corrective 

 factor theory of experimental parthenogenesis has no logical status 

 as an explanation of fertilization. Fertilization can be explained 

 only by observation and experiment on ova and sperm during 

 fertilization. It can not be explained by mere analogy of the 

 processes in experimental parthenogenesis. 



But the superficial cytolysis-corrective factor theory as an ex- 

 planation of experimental parthenogenesis itself is open to grave 

 suspicion. First, the corrective factor may operate alone and give 

 results. In the second place, the corrective factor, says Loeb, 

 may act first when, according to the theory, there is nothing to 

 correct, and the cytolytic agent may follow presumably to vitiate 

 the action of the corrective factor. Again, as I have previously 

 pointed out, the theory is largely built on the assumption that the 

 proper exposure to butyric acid for inducing membrane formation 

 is cytolytic because an over-exposure is lethal. This does not fol- 

 low. One might just as well argue that since stimulation of the 

 cardiac components of the vagus causes cessation of the heart beat 

 the normal function of these fibers is to kill the animal. 



Nevertheless some may hold, despite these criticisms, that the 

 superficial cytolysis-corrective factor hypothesis is still a valid 

 explanation of experimental parthenogenesis ; that while it is true 

 that most marine ova need but a single agent to induce develop- 

 ment, eggs of sea-urchins need two. If, now, we can show for 

 the egg of Arbacia that a single agent acting alone can induce both 

 membrane formation and cleavage, then again is the famous theory 

 put to question. And if, more than this, we can show that this 

 single agent is the corrective factor anti-cytolytic, if you please- 

 then the superficial cytolysis-corrective factor theory must be re- 

 jected, for the egg of Arbacia at least, as an explanation not only 

 of fertilization, but also of experimental parthenogenesis as well. 



The present communication aims to present data, accumulated 

 during the season of 1921 at the Marine Biological Laboratory, 

 Woods Hole, Mass., to show that hypertonic sea-water alone act- 

 ing on the uninseminated eggs of Arbacia will give membranes, 

 cleavage, and viable surface-swimming plutei scarcely to be distin- 

 guished from those resulting from normally fertilized eggs. 



