174 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
Shortly afterward my attention was again drawn to the 
connection between membrane formation and cytolysis, when 
performing experiments upon the effeet of benzol and amylene 
upon the unfertilized sea-urchin eggs. Here too it turned out 
that the first effect of these hydrocarbons was, as Herbst! had 
already observed, the formation of a fertilization membrane, 
but this was followed almost at once by the cytolysis of the egg.” 
I found that if the eggs are removed soon enough from the 
sea-water containing benzol or amylene, they can be caused to 
develop into normal larvae after a short treatment with a hyper- 
tonic uae A similar result was obtained in experiments 
upon the artificial membrane formation by the higher fatty 
acids, and we shall return to this again.* 
We wiil now discuss the series of different cytolytic reagents 
from the point of view of their membrane-forming effect, and 
we will start with the first group, that of the specific haemolytic 
substances such as the glucosides (saponin, solanin, digitalin), 
bile salts, and soaps; in this group belong the foreign sera, 
to the consideration of which a special chapter will be devoted. 
We shall start with a description of the effect of saponin upon 
the sea-urchin egg. 
2. Figs. 39 to 45 are camera drawings of the changes of an 
egg in a saponin solution (8 drops of a 3 of 1 per cent saponin 
solution in sea-water to 5 c.c. of sea-water). Fig. 39 gives the 
size and the appearance of the egg immediately after trans- 
ference to the saponin solution (at 9:07 a.m.). Membrane 
formation (Figs. 40 and 41) started four minutes afterward, 
and at Fig. 42 a normal fertilization membrane had been 
formed. Five minutes later, cytolysis starts, and indeed in 
this case it depends upon a process which superficially and 
in the beginning resembles membrane formation. For at G@ 
1 Herbst, Biol. Centralbl., XIII, 14, 1893. 
2 Loeb, ‘‘ Ueber eine verbesserte Methode der kiinstlichen Parthenogenese,”’ 
Untersuchungen, p. 340. 
3 Ibid., p. 342. 
mY 
