STUDIES IN ARTIFICIAL PARTHENOGENESIS. 347 



in the eggs of the sea-urchins, offers the following explanation. 

 A jelly exists between the surface of the egg and the elevated 

 membrane, for the distance between the egg and membrane 

 always remains uniform on all sides. The pushing out of the 

 membrane is due to the absorption of water by this gel. Herbst 1 

 in a study of membrane elevation in sea-urchin eggs, supports 

 Fol's interpretation. A similar view is likewise expressed by 

 Krassuskaja and Landau 2 and by R. Hertwig. 3 Nevertheless, 

 the view is sometimes regarded as due to Loeb, who first proposed 

 it in 1908. Let us follow the latter's reasoning a little more 

 closely. 



In 1900, he regarded membrane elevation as due to coagulation. 

 In 1905, 4 he thought of it as a secretion. In 1907 he began to 

 consider it as due to liquefaction. He first proves that in general 

 the same types of treatment will produce haemolysis of the red 

 blood cells and the throwing off of a membrane in Arbacia. 

 Then he proceeds to adopt the current theory of haemolytic 

 action to account for the membrane elevation. Koppe and 

 others had attempted to show that the solution or liquefaction 

 of lipoids was necessary for haemolysis. Accordingly, Loeb 5 

 expresses the view that membrane elevation is primarily due 

 to a solution of lipoids at the periphery. This view was also 

 taken up in Loeb's laboratory by v. Knaffl-Lenz, 6 who brought 

 forth evidence that the lipoid in question was lecithin. But the 

 actual force which produced the membrane elevation Loeb be- 

 lieves to be due to the swelling of a colloid. He conceives of this 

 colloid as being given off at the time of fertilization and imme- 

 diately swelling and thus distending the membrane. This does 

 not accord with his previous statements that the unfertilized 

 egg is naked, but Loeb surmounts this difficulty by assuming an 

 " Oberflachenlamelle " or a differentiated surface layer. In 1909, 

 Loeb 7 is no longer certain that solution of lipoids is necessary, 



1 C. Herbst, loc. cit. 



2 Krassuskaja and Landau, Biol. Centralbl., XXIII., 613 (1903). 



3 R. Hertwig in O. Hertwig's Handbuch der Entwicklungslehre der Wirbeltiere, 

 I. (i), p. 484- 



4 Univ. Cal. Publ. Physiology, II., 123 (1905). 



5 Loeb, Arch. f. d. ges. Physiol., CXX., 196 (1908). 



v. Knaffl-Lenz, Arch. f. d. ges. Physiol., CXXIIL, 279 (1908). 

 7 Loeb, "Chem. Entwicklungserregung," p. 248. 



