558 FRANK R. LILLIE 



in sea-urchin eggs without membrane formation but the devel- 

 opment tends to be quite abnormal. Loeb has observed that 

 membrane formation may be induced in such eggs after they have 

 reached even the 8 or 16-celled stage by addition of sperm; they 

 are still fertilizable, so far at least as the cortical changes are 

 concerned. It is fair to assume in such a case that the lack of 

 membrane formation is evidence of persistence of free fertilizin 

 in the cortex, for the only cases in which I found this substance 

 absent from mature eggs are eggs with membranes formed. This 

 case, therefore, need offer no difficulty for the contention that the 

 fertilizin is necessary for fertilization. 



On the other hand, Loeb's method of treatment with fatty 

 acids leads to membrane formation and such eggs are non-fertiliz- 

 able, as Loeb states and I have myself observed. Loeb, however, 

 goes on to assert that if such eggs are shaken so as. to destroy the 

 membrane and if sperm is then added, a new membrane is formed 

 and the typical development of sperm-fertilized eggs follows. 

 This would seem at first sight to run counter to my theory unless 

 it could be shown that membrane-formation by butyric acid 

 differed from membrane formation by sperm in not causing ces- 

 sation of fertilizin production. However, as I shall show im- 

 mediatelj^, the production of fertilizin does cease after the forma- 

 tion of good membranes by butyric acid. 



It is necessary, therefore, to examine Loeb's statement rather 

 carefully. It is as follows : 



Dr. Kupelwieser und ich stellten diesen Versuch an, indem wir die 

 Membranbildung bei unbefruchteten Eiern mittels Buttersaure her- 

 vorriefen, diese Membran dann unmittelbar ndch Bildung derselben, 

 durch Schlitteln der Eier zum Platzen brachten und sofort Samen zufiig- 

 ten. Die Eier bildeten eine neue dem Zijtoplasma dicht anliegende 

 Membran und furchten sich mit einer der Samenbefruchtung entsprech- 

 enden Geschwindigkeit, und Zwar zunachst ausnahmslos in zAvei Zellen. 

 (Loeb '09, p. 210; italics mine). 



It is implied that such superposition of fertilization on parthe- 

 nogenesis would not take place unless the experiment was per- 

 formed immediately after membrane formation. Presumably 

 some fertilizin remained unbound for a short time and on account 



