Dr. ‘idlson 5, Stone,
Dept. coclogy,
University of Texas,
Austin, Texas.

Dear Dr. Stone,

Enclosed are the two canuscripts you have sent. Thunk you for the opportunity
of seeing them. The work 4s very impressive, and I hope you will not regard these
criticisms as at sll derogatory. However, I feel that the concept that the mtations
result from the assimilation intc the gene of nseudo-metabolites is only one
hypothesis among miny, although as good a working basis as any of then likewise.

As to the catalase paper, I haven't very much te comment. On p.5, L8 3d Par.,
I think it would be clearer to write "We may therefore conclude that at such a con
Gentration....# for"@bviously, at such....."

I am not clear what the status of the peroxide in irradiated broth my be.
Can 1-5 pom H.,0., be detected with T1C1, when added to broth? hat proportion of
peroxide udde broth is recoverable with cutaluse? Does your catalase react
with organic peroxides (according to Sumer and Somers, the poecificity of catalase
4s controversial.)
Perhans the ost dubious paragraph is on p. 7 referring to the mitaggenic
effects of azide. The point is important enough (from the point of view of "spontaneaus
mutations") that 1 think 1) a somplete account of the expsrinent should be given
here, and 2) soze definite authority given for the assertion that cells inhibited
by azide accumulate peroxide. It might be mentioned that azide is not entirely
specific for iron enzymes; 2ccording to Spiegelman, e.g., it interferea with
phosphate transfer in the sane way as dinitrophencl. Carbon moroxide or cyanide
would be mere suitable,

Professor Tatum and I have not had much success with transformations in LE. eoll,
for which reason I am still anxious to hear of Wyss' results in this direction.

Thank you again for the privhlege of seeing these papers in manuscript.

Yours sincerely,

Joshus Lederberg
Agsistant Professor of Genetics