244 PROBLEMS OF FERTILIZATION 



is repeated at least four or five times, the nucleus all 

 the time increasing in bulk. The phenomena then 

 become less regular but still continue to be rhythmical, 

 and no cleavage results. 



The activated egg, thus unable to divide, spends its 

 energy in these fruitless ways and ultimately breaks 

 down or cytolyzes, as does any sufficiently abnormally 

 directed egg. 



How does the second treatment with hypertonic 

 sea-water save the life of the egg ? Briefly, it does this 

 by giving the egg the capacity for regular division and 

 thus directing the energies of the egg into normal chan- 

 nels. Morgan (1896, 1900) and Wilson (1901), among 

 others, had long ago noted that unfertilized eggs of 

 sea urchins react to hypertonic sea-water by forming 

 asters apart from the nucleus. Herlant has shown that 

 one of these cytoplasmic asters, together with the mon- 

 aster associated with the egg nucleus, form an amphi- 

 aster which initiates regular division of the egg nucleus. 

 From this time on everything moves normally. 



It is therefore clear that the changes underlying 

 membrane formation do not involve progressive cytol- 

 ysis; it is the processes of activation aroused by the 

 cortical changes that are responsible for the final death 

 of the egg in the absence of proper co-ordination of 

 nuclear and cell division. It is therefore very doubtful 

 that the changes underlying membrane formation itself 

 should be regarded as cytolytic, unless by extension of 

 the usual meaning of the term "cytolysis." The nature 

 of the cortical changes underlying membrane forma- 

 tion seem to the writer still to be obscure, but it is 

 inadvisable to use a term with a purely pathological 



