XVII 

 MEMBRANE FORMATION AND CYTOLYSIS 



1. In this chapter we shall show that all haemolytic agents 

 also cause membrane formation. We find usually that a short 

 exposm-e of the egg to such a reagent leads only to membrane 

 formation, a longer one to cytolysis. According to Koppe, 

 besides electricity and heat, there are five classes of reagents 

 that cause cytolysis; they are: (1) certain specific substances, 

 such as glucosides (e.g., saponin) or bile salts; (2) a number 

 of fat-solvents, such as benzol, ether, and alcohol; (3) distilled 

 water; (4) acids; (5) bases. We have already seen that the 

 two last-named substances lead to membrane formation, and 

 we shall show that the same is true for the others, and that with 

 proper after-treatment this membrane formation leads to the 

 development in the sea-urchin egg (and the eggs of other 

 forms) . We can therefore say briefly that all haemolytic agencies 

 effect the activation of the unfertilized egg, and this activation con- 

 sists in a cytolysis of the cortical layer of the eggs. 



I first noticed the connection between membrane formation 

 and cytolysis when in 1904 I was trying to discover why no 

 typical membrane was formed in my original method of artificial 

 parthenogenesis by hypertonic solutions. In the course of these 

 investigations it happened that when the osmotic pressure was 

 high enough, e.g., with 1| m solutions of NaCl or cane sugar, the 

 unfertilized eggs produced a splendid fertihzation membrane; 

 but this membrane formation was followed almost at once by 

 a cytolysis of the whole egg.^ A similar phenomenon occurs 

 when the eggs are placed in distilled water; for they also form 

 membranes and are immediately afterward transformed into 

 "shadows." 



' Loeb, "Ueber Befruchtung, kiinstliche Parthenogenese und Zytolyse des 

 Seeigeleies," Pfliiger's Archiv, XCIII, 257, 1904; Untersuchungen, p. 288. 



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