The adrenal of the male tammar wallaby first appears at day 21 of embryogenesis as a nodule of tissue lying close to the anterior pole of the kidney. The nodule consists of adrenocortical tissue in that its cells contain an active 3 beta ol-steroid dehydrogenase from about day 22 of embryogenesis. From day 22 of embryogenesis until at least day 20 of pouch life a sympathetic nerve plexus is adpressed to the medial side of the adrenal. Cells migrate from the plexus through pores in the capsule of the gland and intermingle with the cortical cells. By day 7 of pouch life some of the invading cells display a chromaffin reaction and by day 60 have formed a distinct medulla. The cortex shows the beginnings of zonation by day 60 of pouch life but the three adult zones are not seen until day 200.

Adrenal glands from normal male and female brush-tailed possums (Trichosurus vulpecula) were weighed and sectioned to investigate reported changes in the relative size of the hypertrophied region of the cortex during the reproductive cycle. Total adrenal gland weight in normal females averaged 120 mg/kg body weight and the hypertrophied region occupied 40% of the gland volume. No significant variation was found in these figures between glands from pregnant, lactating and cyclic possums . In addition, no cyclic pattern of cellular changes was found in the hypertrophied region. These results differ from views expressed in the current literature which are based on the original description of the hypertrophied zone.

A histochemical study has been made of groups of cells lying adjacent to the blood vessels of the kidney of Neoceratodus forsteri. The cells contain lipid droplets of varying sizes, stain positively for cholesterol and its esters and contain 3betaol-steroid dehydrogenase activity. Similar cells have previously been described in another dipnoan fish, Protopterus, and in a urodele, Pleurodeles waltlii and are considered to be the adrenocortical tissue of these species. Because of the histochemical characteristics of the cells together with their location, we conclude that they represent the adrenocortical homologue of N. forsteri. As is the case in Protopterus, no chromaffin tissue was detected in the kidney of N. forsteri.