MEMBRANE FORMATION AND CYTOLYSIS 181 



repeatedly, and one hour later placed in hypertonic sea-water 

 from which they were transferred to ordinary sea-water after 

 thirty to fifty minutes. A number of the eggs which had 

 formed membranes developed into larvae. 



These experiments prove that the membrane formation 

 induced by soaps can also set up development. This method, 

 however, has little to recommend it for practical purposes, 

 because the cytolytic effect of the soap is so strong. Eggs 

 treated with soap show a much greater tendency to cytolysis 

 than those treated with a low fatty acid. 



4. Another group of haemolytic agents is formed by fat- 

 solvents, such as benzol, toluol, amylene, chloroform, aldehyde, 

 ether, alcohol, etc. It has already been mentioned that when 

 benzol, toluol, and amylene are dissolved in sea-water only 

 a trace of them is soluble they produce a membrane forma- 

 tion in eggs, which is followed practically at once by cytolysis. 

 Hence the specific fat-solvents are of little use for artificial 

 parthenogenesis. The same principle, however, that is found 

 in the saponin group also applies here: by working quickly, 

 removing the eggs from the benzol or amylene sea-water as soon 

 as membrane formation has taken place, and transferring them 

 to ordinary sea-water, it can be demonstrated that a certain 

 percentage of eggs form membranes, without undergoing 

 cytolysis. These eggs can be caused to develop into larvae 

 by treating them subsequently with hypertonic sea-water. If 

 they are not treated with hypertonic sea-water, they do begin 

 to develop, but they disintegrate before reaching the larval 

 stage. 



Owing to the importance of this subject, we will describe the 

 cytolysis of the sea-urchin egg under the influence of a reagent 

 belonging to this group. Figs. 46 to 51 show the behavior of 

 the sea-urchin egg in a mixture of 45 c.c. of sea-water +5 c.c. 

 of m/100 salicyl aldehyde. A beautiful membrane formation 

 first takes place (Fig. 49); but then cytolysis starts with the 



