GENERAL PROPERTIES OF THE ECTOPLASM 



is many times more susceptible to dilute sea-water during 

 the period of membrane separation than the fertilized 

 e^g before or after this separation, or than the unfertilized 

 &gg. The egg is never again so susceptible, although 

 during the cleavage-cycles it exhibits rise and fall in 

 susceptibility which may be correlated with the rhythm 

 of nuclear division. We may consider in detail this sus- 

 ceptibility to hypotonic sea-water first as seen in the egg 

 of Echinarachnius. 



If to a drop of sea-water containing unfertilized eggs of 

 Echinarachnius mounted under low power of the micro- 

 scope, tap or distilled water be added, one can observe that 

 the eggs take up water, swell, and finally break down in 

 about two minutes. For example: the time of disintegra- 

 tion in tap water for lots of eggs from ten females was as 

 follows : 



Number of females 



Time in seconds to disintegration of the 

 eggs while in tap water 



270243 



3 

 60 



4 

 113 



5 

 150 



148 



7 

 256, 



247 



9 



155 



ID 



240 



The rate of disintegration in eggs from these same females 

 exposed to the action of tap water, five to ten seconds after 

 insemination, was about the same. Eggs from the same 

 females exposed to the action of tap water two minutes 

 after fertilization, i.e., after the membranes are completely 

 off the eggs, withstood the exposure even better than the 

 unfertilized eggs. But with the beginning of membrane 

 separation, twenty to thirty seconds after insemination, 

 the picture is quite otherwise, for then the eggs are highly 

 susceptible. The following table gives the results of such 

 an experiment made on eggs of the same females as were 

 used in the above described experiment. 



Once it was well established by experiment with tap 

 water that the period of high susceptibility falls in exactly 

 with the period of membrane separation, attention was 



log 



