Genie Control of Development 301 



Even assuming that the methods of measuring permit the estab- 

 Hshing of the facts underlying this theory (which is not generally 

 conceded), it is very difficult to imagine how such vague concepts 

 could be made to account for specific features, apart from the fact 

 that the variability of DNA claimed, but without a clear scheme of 

 distribution, is not of the nature of an agent controlling orderly 

 di£Ferentiation. Since the basis of the whole argument is rather doubt- 

 ful, and since such ideas as genes producing DNA are anything but 

 clear, and are difficult to reconcile with our knowledge of the role of 

 DNA, it seems that the material can hardly be advocated as an indi- 

 cation of intranuclear change as cause of differentiation. 



From a very different and rather original angle, P. B. Weisz ( 1951 ) 

 arrived at the postulate of intranuclear differentiation controlling 

 (partly) processes of developmental differentiation. His work deals 

 with ciliate protozoa. He starts with Dobell's assumption, now 

 generally accepted, that a ciliate is not a unicellular but a noncellular 

 organism, which, therefore, must be compared to an entire metazoan 

 organism. The macronucleus of ciliates is known to be the product of 

 a differential division of the fertilized micronucleus, the other division 

 product being the new micronucleus (see, however, the variants em- 

 phasized by Sonnebom, 1955). It is further known that the macro- 

 nucleus contains what is assumed to be all the genie material as 

 regeneration, and all other life processes can go on in the absence of 

 the micronucleus, which thus represents only the germ line of Meta- 

 zoa. (Sonneborn has shown that the macronucleus contains the killer 

 locus; hence the general result applies also to the individual mutant.) 

 The macronucleus, however, does not remain simple, but forms by in- 

 ternal divisions a combination nucleus consisting of many subnuclei, to 

 which may be applied Hartmann's term, polyenergid nucleus, recently 

 demonstrated again in Radiolaria ( Hartmann, 1952 ) . This is not to be 

 mistaken for the polytene nucleus discussed above, which never could 

 be unscrambled into single nuclei, as may be done for the polyenergid 

 nucleus. This polyenergid macronucleus contains also, as expected, 

 the proportional amount of DNA. (However, Kimball, 1953, does not 

 find this polyenergid condition, a difference of opinion which will 

 have to be resolved.) 



Weisz asked himself whether all these subnuclei (which in cell 

 division are simply split at random) are and remain genetically 

 equivalent. In two species of Stentor and Blepharisma it was ascer- 

 tained that the micronuclei are not needed for regeneration. The 

 macronucleus is monilfform in both. By microdissection the individual 



