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Observations of CN and CH band strengths among a random sample ofmain-sequence turn-off stars (+3.9 < MV < +4.6) in the globular cluster 47 Tuc(NGC 104, C0021-723) were made with the CTIO Argus fiber spectrograph for thepurpose of determining the ratio of CN-strong to CN-weak stars andinvestigating the behavior of CH relative to CN. Of the 20 turn-off stars, 12were found to be CN-strong while 8 appear to be CN-weak. This ratio ofCN-strong to CN-weak stars is similar to the ratios found among the moreluminous 47 Tuc stars and implies little change in the overall distribution ofCN with evolutionary state, although the present sample size is small. Ageneral anticorrelation between CN and CH is also observed in that the CN-weakmain-sequence stars all (with one possible exception) exhibit strong CH bands -a trend similar to that found among the brighter stars. That these variationsoccur among such relatively un-evolved stars and that the overall CNdistribution appears to be independent of evolutionary state presents seriouschallenges to internal or mixing theories of their origin. We therefore suggestthat at least some component of the C and N abundance inhomogeneities observedamong the brighter (more evolved) stars of this cluster appears to have beenestablished prior to the commencement of evolution up the red giant branch.Comment: 11 pages in uuencoded compressed postscript (including all figures),  to appear in the December 1994 Astronomical Journa

Anticorrelated CN and CH variations on the 47 Tucanae main-sequence turnoff