AMINO ACIDS 97 



types of investigations to systematics. Although Buzzati-Traverso's 

 work included examination of fluorescent substances in addition to 

 amino acids, the former class was probably a rather heterogeneous 

 assemblage of undefined substances. These may be considered here 

 since the principles concerned are independent of the nature of the 

 compounds compared. Fruit flies (Drosophila) were studied inten- 

 sively, but Buzzati-Traverso also included some plant studies, as will 

 be disclosed. The flies were fed a standard diet and chromatographed 

 by mashing the individual flies directly on paper. It was not stated 

 that the Drosophila compared were isogenic. The ninhydrin patterns 

 (revealing amino acids) of different Drosophila strains were said to be 

 similar, but with respect to fluorescent spots, males and females ex- 

 hibited distinct differences. Since later work by Fox (1956) on sex dif- 

 ferences in Drosophila elaborates this point somewhat, and will in 

 turn be discussed, no description of these sex differences is necessary 

 here. Of more importance for this discussion are the results of 

 Buzzati-Traverso's comparisons of a series of mutants with corre- 

 sponding wild type flies. As a background, it should be noted that 

 Hadorn and Mitchell (1951) had undertaken a chromatographic 

 study of fluorescent patterns of Drosophila mutants in eye color and 

 body color. Although conspicuous changes in the fluorescent patterns 

 occurred in different developmental stages, Hadorn and Mitchell, in 

 their early work reported no significant differences in the fluorescent 

 patterns of either eye color or body color mutants, as opposed to wild 

 type, at any stage examined. More recently, however, with improved 

 chromatographic techniques for the separation of pteridines (which 

 include the Drosophila eye pigments), distinctive chromatographic 

 differences are now correlated with a number of eye color mutants 

 (Hadorn, 1962). Buzzati-Traverso used a group of m.orphologicgd 

 mutants rather than biochemical mutants (that is, the overt 

 phenotypic expression was morphological rather than biochemical). 

 By Buzzati-Traverso's interpretation of his results each of the strains 

 tested gave a distinctive fluorescent pattern, and each genotype had 

 a characteristic biochemical pattern. According to the author the 

 heterozygotes could always be detected, though the morphological ex- 

 pression of the gene indicated dominance. The present writers, after 

 examining the illustrations in the Buzzati-Traverso paper, have some 

 reservations concerning his interpretation. It appears possible, if not 

 probable, that the pattern differences were in part artifact. In some 

 cases, for example, two patterns may appear to be different, but by 

 our interpretation the only difference that is apparent is a shifting of 

 the Rf values of the same series of spots upward in certain cases. 

 Perhaps, in the photographic reproduction the detafls were lost, but 



