Author index for volume 91

We have induced teratocarcinomas in $\text{C3H}\text{He}$ strain mice by extra-uterine transplantation of egg cylinder stage embryos. Embryonal carcinoma cell lines with male karyotypes were isolated from three different tumor lines. One of the cell lines has a normal karyotype. The Y chromosome in each of two lines tested replicates late during the S phase of the cell cycle at the same time as Y chromosomes in male somatic cells.     

R Plasmids R91 and R91a from Pseudomonas aeruginosa Share Only the Gene for Carbenicillin Resistance

Plasmid R91a of Pseudomonas aeruginosa strain 9169 is homologous with RP1. Plasmid R91 carried by the same strain is related in the Tn1 region but is otherwise unrelated to R91a.