60 CHARLES D. SNYDER. 



it is in the other. For since the beautiful demonstration of 

 Chambers 8 there can be no doubt that the fertilization membrane 

 is a preexistant structure. One may take the limit in the 

 swelling, therefore, to be the degree of permeability and elasticity 

 of the membranes in both cases. 



What has just been said of the eggs subjected to hypertonic 

 solution appears also to be true of the eggs subjected to citric acid. 

 For in this latter case the egg-cytoplasm also swells coextensively 

 with the egg- membrane. It will be remembered that in these 

 eggs the membrane could be seen bridging the furrows between 

 the cells after cleavage, in this respect differing from the hyaline 

 membrane that is observed to dip down and follow the furrow 

 closely. 8 The limit to swelling in the artificially parthenogenetic 

 Asterina egg thus also lies in the egg (fertilization) membrane. 

 Only, the citric acid treatment seems to render the membrane 

 somewhat less permeable to water or less elastic, or both less 

 permeable and less elastic, than does the treatment with normal 

 sperm. 



In conclusion it may be added that while the above observations 

 contribute little or nothing of a decisive character to the problem, 

 they nevertheless do add to the attractiveness of the space-time 

 method. With the newer technique a thoroughly systematic 

 application ought to yield results not only decisive but also 

 important. 



THE JOHNS HOPKINS UNIVERSITY, 

 December 18, 1924. 



'Chambers. BIOL. BULL., Vol. XLL. pp. 318-350, 1921. 



