SITES WITHIN THE CELL 



51 



morphology of the umbrella which develops corresponds to the strain of 

 the nucleate part. Since the structure of the umbrella is a hereditary char- 

 acter, it is quite clear that genetic determinants are provided by the 

 nucleate moiety. This is important for the present discussion. 



In his early studies, Hammerling (1934) had already observed that 

 enucleated fragments can elongate for some time and that the number of 

 chloroplasts increase. This made it probable that proteins were formed in 



adult 

 cap 



Zygote 

 ^;^l^ 2 doys 



8 days 

 Fig. 21. Life cycle of Acetabularia mediterranea (courtesy of J. Brachet). 



cytoplasmic fragments. Direct biochemical studies by Brachet and his 

 collaborators established that the rate of incorporation of i*C02 or of 

 labelled glycine into the proteins of Acetabularia is not changed in the 

 enucleate fragment. The rate of incorporation is the same in both halves at 

 least during the first two weeks after cutting (Brachet and Chantrenne, 

 1951, 1952; Chantrenne et ah, 1953). The total protein content increases at 

 the same rate in nucleate as in non-nucleate fragments (Vanderhaeghe, 



