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Antibodies to egg-yolk semen diluent antigens were isolated from the majority of samples from the vagina, uterus and serum of cows which had received repeated artificial inseminations with semen diluted in egg-yolk diluent. The vagina was the site from which antibodies were isolated most frequently. There was evidence that the titres of antibodies in the genital tract resulted in part, at least, from local antibody production by the vaginal and uterine tissues.Samples with titres to egg-yolk diluent antigens, when tested in vitro, caused mixed agglutination of homologous spermatozoa diluted in egg\ x=req-\ yolk diluent, while non-specific head-to-head agglutination was seen when the spermatozoa had been diluted in saline. When the cows were inseminated with homologous semen diluted in egg-yolk diluent, the fertility of animals which had uterine titres was significantly lower (P\ m=ge\ 0\m=.\05) than that of animals which had no titres.Antibodies to homologous bovine semen were detected in very few uterine samples from animals which had received repeated inseminations.

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The data collected during 26 days of cattle watching have been examined. Differences in the distribution of the habits, and of the length of time spent on each habit, larger than those recorded by other workers, are given. Possible explanations for these differences are discussed; part of the variations may have been caused by individual behaviour, and part by changes in climatic conditions. It is concluded that the major cause of variation is the difference between the herbage quantity and quality on the different pastures.