these cells, its tail being derived from other 

 portions of the cell. 



It follows that not only eggs but also sperms, 

 prior to their union in fertilization have passed 

 into a reduced or single state as regards their 

 chromatin constituents, whereas the fertilized 

 egg, and the organism which develops from it, 

 is in a double condition. It will be convenient 

 to refer to the single condition as the N condi- 

 tion, the double as the 2 N condition. 



From a wholly different source we have 

 evidence strongly confirmatory of the conclu- 

 sion that the fertilized egg contains a double 

 dose of the essential nuclear material. By arti- 

 ficial means it has been found possible to cause 

 the development of an unfertilized egg. The 

 means employed may be of several different 

 sorts, such as stimulation with acids, alkalies, 

 or solutions of altered density. In such ways 

 the development has been brought about of the 

 eggs of sea-urchins, star-fishes, worms, and mol- 

 lusks, which normally require fertilization to 

 make them develop. 



The sea-urchin egg has been made to develop 

 more successfully than any other. This has 



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