INFLUENCE OF HYDROGEN ION CONCENTRATION. 311 



the even contour of the egg is lost. As Chambers (6) has shown 

 by microdissection, the granules in the dead egg are disintegrative 

 products and not comparable to the granules in the living egg. 

 They are no longer glutinous or adhesive ; the egg has entirely lost 

 its original homogeneity and is held together only by the investing 

 vitelline membrane. Gradually this disintegrative mass imbibes 

 water and swells within the vitelline membrane, becoming a more 

 or less vacuolated liquid mass. Ultimately, the membrane breaks 

 and the contents are dissipated in the sea water. 



When Asterias eggs are allowed to age in acid and alkaline sea 

 water, the transformation of the nucleus and the subsequent gran- 

 ulation of the cytoplasm occurs most rapidly in solutions more 

 alkaline than sea water, and at about the same rate from pH 8.0 

 to 5.4. At acidities greater than pH 5.4 the nuclear transforma- 

 tion is perceptibly retarded and the cytoplasm acquires a granular 

 appearance which differs from that of eggs aged in more alkaline 

 solution principally by a diminished degree of discoloration. 



From pH 5.4 to 6.2 many eggs are observed which contain, 

 instead of a single vesicular nucleus, two, three or more smaller 

 contiguous vesicles. Such eggs are observed much less frequently 

 in solutions more alkaline than the optimum, pH 6.2. These 

 polyvesiculated eggs will, when returned to sea water and insem- 

 inated, lift normal, turgid fertilization membranes in 3 to 5 min- 

 utes, and will usually cleave simultaneously into several blasto- 

 meres. If not inseminated when returned to sea water, a very 

 small per cent, of the polyvesiculated eggs will fragment once or 

 twice, the vesicles apparently being distributed among the frag- 

 ments. Although the process of migration of these vesicles into 

 the fragments prior to cleaving was not observed, they appear 

 to be causally related to the process of fragmentation. Fertiliza- 

 tion membranes are not formed spontaneously on the polyvesicu- 

 lated eggs either in the acid by exposures of two to three hours, 

 or when returned to sea water ; though a few eggs will form fertil- 

 ization membranes if left in the acid solutions for considerably 

 longer periods, 4 to 6 hours. The fragments are held together by 

 a delicate membrane bridging the furrows ; this may be the vitel- 

 line membrane of the unfertilized egg. 



The nucleus of the Arbacia egg acquires a vesicular appearance 



