Summary Rufous night herons, Pacific herons, little egrets and intermediate egrets were experimentally infected with Murray Valley encephalitis, Kunjin or Japanese encephalitis viruses. Viraemias of at least one day's duration were detected in all birds except two intermediate egrets inoculated with a very low dose of Kunjin virus and one rufous night heron inoculated with Japanese encephalitis virus. There was usually a viraemia of 3 to 5 days' duration commencing on the first or second day and continuing until day 5 or 6 and rarely until day 7. Maximum titres tended to be higher in young birds, up to 2–5 months of age (104–105 mouse LD50/ml), than in older birds more than 8 months of age (103–104 mouse LD50/ml). Significant differences in maximum viraemia titres were not observed in the different species or between Murray Valley encephalitis and Kunjin viruses. Japanese encephalitis viraemias were significantly lower, but this was probably due to the high mouse brain passage level of the strain used. The onset of viraemia was earlier in intermediate egrets than in rufous night herons inoculated with similar doses of Murray Valley encephalitis virus, but no difference in the susceptibility to infection was observed. With Kunjin virus there was a significant difference in the susceptibility of intermediate egrets and rufous night herons, with rufous night herons being more susceptible to infection with low doses of virus. This difference in threshold of infection, if it extends to other species with both Kunjin and Murray Valley encephalitis viruses, may, in part, be an explanation for the greater incidence of natural infections observed in rufous night herons compared with other species and orders of water birds.

THE Sierra Madre or Bailey's Sparrow, Xenospiza baileyi, was described as a new genus and species from the high mountains of Durango and Jalisco less than 35 years ago (O. Bangs, Proc. •Vew England Zool. Cl., 12: 85-88, 1931). It has since been considered rare, and even 19 years ago, when F. A. Pitelka (Condor, 49: 199-203, 1947) described a new subspecies, only 11 specimens were known, of which he had at hand only 1 from La Cima, Distrito Federal, and 3 from western Mexico. Today the population from the sacaton bunch grass areas of La Cima, in the pass between the Valley of Mexico and Cuernavaca, is well represented by series in the collections of Phillips and the University of Minnesota Museum of Natural History. These series include specimens in all the plumage stages from stubby-tailed juveniles to worn adults and those having recently completed the prebasic molt. Other specimens are scattered through several museums in the United States. The population of Durango is now represented by additional specimens in the collection of the Robert T. Moore Laboratory of Zoology, Occidental College. With the accumulation of this material, and notes from several seasons' field work by the authors, it is a propitious time to gather together the information on this restricted endemic Mexican sparrow.

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Venezuelan equine encephalitis virus was recovered in the state of Veracruz, Mexico, during July and August 1963 from young, weaned hamters, and from baby mice used as sentinel animals, and from Culex mosquitoes. Hamsters of 5 to 10 weeks of age became infected in nature and were nearly as susceptible as suckling mice to subcutaneous inoculation of VEE virus.

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