ACCORDING to the cyclol hypothesis of peptide structure1,2, intact peptides may have poly cyclic structures which can be visualized, in part at least, as polycyclizations of peptide chains by means of [CO,HN to C(OH)-N] proton transfers. Here the H of the NH group of one residue is transferred to the CO-group of another : a N-C bond forms and the CO-group is replaced by a tertiary carbinol3. There result multiple as well as the CO-NH single peptide groupings. Fig. 1 shows some structures which emerge when consideration is confined to (1,6) and (3,7) transfers and piperazine and hydantoin rings are formed.