Abstract: Summary One hundred and forty-four naive virgin female golden hamsters were each given a single 15 min test with three pups aged from day 1 (<24 hr) to day 18. A group of eight females was tested with each age of pup. Pups aged from day 1 to day 6 were generally attacked like prey, killed and eaten. Pups of intermediate age (day 6 to day 10) were usually initially attacked but this was often followed by maternal responses. The females', behaviour with the oldest pups suggested that they were being treated as strnge adult intruders. This result differs from that of a similar experiment with mice in which the youngest pups were found to be the most effective for eliciting materal responses. An explanation for this difference in terms of the evolutionary history of the golden hamster species is proposed.

Abstract: Thin-layer chromatography, acetylation of reference and unidentified glucocorticosteroids, u.v. absorption and fluorescence induced in sulphuric acid were used to identify cortisol as the major free plasma glucocorticosteroid in the horse (Equus caballus), with cortisone and corticosterone as minor glucocorticosteroids. Deoxycorticosterone was also identified. The plasma ratio for free cortisol: cortisone: corticosterone was 16:8:0·5.The diurnal variation was determined for all three glucocorticosteroids. The highest levels of cortisol and corticosterone were found at 10.00 hr. (260 and 10·3 μg./100 ml., respectively) and the lowest concentration of cortisol at 02.00 hr. The highest level of cortisone occurred at 02.00 hr. (140 μg./100 ml.), and the lowest appeared at 16.00 hr. (65 μg./100 ml.). The maximum plasma concentration of the combined glucocorticosteroids was found at 10.00 hr. (395·3 μg./100 ml.), and the minimum at 20.00 hr. (219 μg./100 ml.).