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hypothesis that A. xylinum is a phylogenetic ancestor of A. 8uboxydan8 thus might imply only that A. xylinum has been able to undergo consecutive loss mutations of two non-essential enzyme systems. An opposing view, namely that evolution proceeded from a simple state to a more complex one, may be more attractive on philosophical grounds. In that case, the interesting possibility has to be considered that the ancestor of Acetobacter was equipped with a mutative potential so broad as to comprise within its range two enzyme systems (respectively for cellulose synthesis and acetate oxidation) which are facultative in Acetobacter but have elsewhere assumed cardinal roles in cellular survival. SUMMARY 1. A cell-free extractofAcetobacterxyltinumfailed to form cellulose from a range of tested substrates. 2. The extract (with added phenazine methochloride) oxidized glucose aerobically to gluconate. When this system was further supplemented with diphosphopyridine nucleotide, it oxidized gluconate to oxogluconate (largely 2-oxogluconate). 3. The extract with adenosine triphosphate oxidized glucose aerobically to carbon dioxide. The extract contained kinases (glucokinase and gluconokinase), phosphoglucomutase, a complete pentosecycle set of enzymes, and a set of enzymes by which triose phosphate could be converted into pyruvate. 4. A scheme of altemate pathways for glucose metabolism that can be operated in an A. xyltinum cell is proposed. The scheme shows a pentose cycle which has several ports of entry and exit. The latter lead from the pentose cycle into a citrate cycle. 5. Biochemical evolution in the genus Acetobacter is briefly discussed. Note added in proof.

RESULTS.Rates of 6-year survival ({ standard error) after isolated bone marrow, 4Memorial Sloan-Kettering Cancer Center, New isolated central nervous system (CNS), and isolated testis relapse were 20% { 2%, York, New York.48% { 4%, and 70% { 5%, respectively. Rates of survival after isolated bone marrow relapse at 0-17 months, 18-35 months, and after 36 months were 6% { 2%, 11% University of Iowa, Iowa City, Iowa. { 2%, and 43% { 4%, respectively. Rates of survival after isolated CNS relapse at 0-17 months, 18-35 months, and after 36 months were 33% { 4%, 59% { 5%, and 72% { 8%, respectively. Rates of survival after isolated testis relapse at 0-17 months, 18-35 months, and after 36 months were 52% { 11%, 57% { 10%, and 81% { 5%, respectively. Rates of survival after combined bone marrow and CNS or testis relapse at 0-17 months, 18-35 months, and after 36 months were 9% { 5%, 11% { 6%, and 49% { 7%, respectively. CONCLUSIONS.Substantial survival at 6 years is evident among several subsets of this unselected group of heterogeneously treated children, namely, those with isolated or combined bone marrow relapse after 36 months and those with isolated extramedullary relapse at any time. Second malignant neoplasms are rare thus far.

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