56 THE PHYSICAL BASIS OF INHERITANCE 



the sea-water. The latter either lacks the presence of a sufficient 

 amount of the ions that are necessary for the mechanics of cell 

 division (Mg, K, HO, or others), or it contains too large a quantity 

 of ions that are unfavourable to this process (Ca, Na, or others), 

 or both. All the spermatozoon needs to carry into the e^g for 

 the process of fertilisation are ions to supplement the lack of 

 the one or counteract the effects of the other class of ions in the 

 sea-water, or both. The spermatozoon may, however, carry 

 in addition a number of enzymes or other material. The ions 

 and not the nucleins in the spermatozoon are essential to the 

 process of fertilisation." 



These remarkable experiments are confirmatory of the general 

 assumption that spermatozoon and ovum are completely 

 equipped potential organisms. Further confirmation may be 

 found in cases of partial parthenogenesis — e.g. the development 

 of drone-bees from unfertilised eggs ; from the close similarity 

 in the history of ovum and spermatozoon respectively ; from 

 the exactly equal way in which the paternal and maternal nuclear 

 contributions are distributed to each cell, during the early stages 

 of cleavage at least. 



When we consider the ovum and spermatozoon as two fully 

 equipped potential individuahties which unite to form the 

 beginning of a new individuality, we see more clearly how, on 

 the one hand, there is a double likelihood of the essential specific 

 characters being sustained, and how, on the other hand, there 

 is every likelihood that the intermingling will lead indirectly, if 

 not directly, to something new. 



§ 8. Inheritance in Cases of Parthenogenesis 



It would be interesting to know with precision what the facts 

 of inheritance are in cases where development proceeds from 

 an unfertilised ovum, particularly in those cases where the 

 parthenogenesis continues uninterrupt'edly for many generations. 



