312 HOMER W. SMITH AND G. H. A. CLOWES. 



on ageing much the same as that of the Astcrias egg. As in the 

 latter case this change occurs in about the same time at all H-ion 

 concentrations from pH 5.0 to 10.0. At acidities greater than pH 

 5.0 there is an increased incidence of eggs in which this nuclear 

 change does not take place. We have not observed the appearance 

 of several vesicles in the Arbacia egg at any H-ion concentration, 

 but our observations would not preclude their existence. 



In solutions more alkaline than pH 9.0 there is a tendency for 

 membranes to lift spontaneously on both Asterias and Arbacia 

 eggs. Prior to membrane formation the cortex of the egg under- 

 goes peripheral disintegration with formation of droplets. Spon- 

 taneous membrane formation decreases with increasing acidity; 

 below pH 7.0 it is rarely observed except when induced in Aster- 

 ias eggs by long exposures to pH 5.4-6.2, as mentioned above. 



CHANGES IN PHYSICAL PROPERTIES. 



The appearance of eggs which have been exposed for a short 

 time to extremely acid or alkaline sea water is markedly different. 

 Alkali treated eggs present a smooth, almost glassy surface, while 

 acid treated eggs are dull and appear to have a finely granulated 

 surface. The slightest amount of manipulation indicates that the 

 alkali treated eggs are soft and more liquid than normal, while eggs 

 treated with acid are more solid. Dr. Chambers has kindly exam- 

 ined the effects of acid and alkali on these eggs by means of micro- 

 dissection. He finds that in acid sea water the thin, delicate vitel- 

 line membrane which normally surrounds the unfertilized Arbacia 

 and Asterias egg is toughened so that it is difficult to tear. This 

 toughened membrane makes it difficult to ascertain mechanically 

 what influence the acid solution may have on the consistency of 

 the egg surface itself, but with non-injurious exposures acid seems 

 to produce no very profound change in the consistency of the egg 

 cortex. Longer exposures lead to a gradual setting or gelation of 

 the cortex (and possibly the egg as a whole), finally accompanied 

 by the loss of its normal transparency. 



In alkali both Astcrias and Arbacia eggs are rendered extremely 

 plastic, soft and liquid by short treatment. This can be shown by 

 shaking the eggs for a uniform time in solutions of increasing 

 alkalinity. Thus when Astcrias eggs are vigorously shaken in sea 



