Fourth Conference of the European Society for Comparative Psychology and Biochemistry, Bielefeld, September 8-11, 19821 Brain Mechanisms.- Sites of Action of Ovarian Hormones in the Regulation of Oestrous Responsiveness in Rats.- Mechanisms of Oestrogen-Progestin Interactions in the Regulation of Lordosis in Female Guinea Pigs.- Diurnal Variations in the Sensitivity of the Brain to Oestrogens: Behavioural and Biochemical Studies.- Catechol Oestrogens: Their Contraceptive Effects and Possible Involvement in Some Reproductive Processes of the Rat.- Cholinergic Regulation of Feminine Sexual Behaviour in Laboratory Rats.- Brain Mechanisms of Maternal Behaviour in the Rat.- Potency and Fertility: Hormonal and Mechanical Causes and Effects of Penile Actions in Rats.- Endorphin-Monoamine Interaction and Steroid-Dependent Behaviour.- ACTH and Grooming Behaviour in the Rat.- 2 Sexual Differentiation.- Genetic Determinants of Sexual Differentiation.- The Interaction of Circulating Oestrogens and Androgens in Regulating Mammalian Sexual Differentiation.- Reproductive Neuroendocrine Rhythms.- Hormonal Influence on Sexual Differentiation of Rat Brain Anatomy.- Hormone-Dependent Brain Development and Behaviour.- Sex Steroids and the Differentiation and Activation of Avian Reproductive Behaviour.- 3 Testosterone Metabolism.- Brain Testosterone Metabolism and Sexual Behaviour in Birds.- Testosterone Metabolism and Sexual Differentiation in Quail.- Hormone-Mediated Behavioural Transitions: A Role for Brain Aromatase.- Hormonal Specificity and Activation of Social Behaviour in the Male Zebra Finch.- Hormones and Different Tests for Aggression with Particular Reference to the Effects of Testosterone Metabolites.- Exposure to Odour During Development and Hypothalamic Metabolism of Testosterone.- 4 Endocrine Cycles.- Male-Female Interaction in the Hamster: Seasonal and Hormonal Effects.- The Control of Sexual Behaviour in the Female Hamster.- Social Factors Controlling Puberty in the FelÓb