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MEREDITH J. CLARK and G. B. SHARMAN

Summary.

Eight females were hysterectomized, three at 5 days, three at 10 days and two at 15 days after oestrus. Seven returned to oestrus at the expected times, 24 to 32 days after the preceding oestrus, and four of these had a subsequent oestrous cycle of normal length. The corpus luteum of hysterectomized animals killed at various stages of the first and second post-operative cycles was compared with that of control non-operated animals killed at similar stages of the cycle and no differences were found. It is concluded that hysterectomy was without effect on the ovarian cycle of the brush possum.

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PATRICIA J. BERGER and G. B. SHARMAN

Summary.

Macropus eugenii exhibits embryonic diapause after fertilization at post partum oestrus. The embryo becomes dormant at the blastocyst stage in response to the suckling stimulus of a young in the pouch during the breeding season and embryonic diapause continues during the non-breeding season in the absence of the suckling stimulus. Dormant blastocysts resumed development when progesterone was injected daily for 3 days. Normal dormant blastocysts were recovered from animals up to 30 days after complete ovariectomy, and progesterone-induced resumption of development occurred in blastocysts up to 21 days after ovariectomy. The termination of embryonic diapause in progesterone-injected marsupials is discussed in relation to the hormonal control of delayed implantation in eutherian mammals.

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G. B. SHARMAN and MEREDITH J. CLARK

Summary.

When plant growth occurred following rainfall after a period of drought in western New South Wales, Australia, 35% of a sample of sixty-five female red kangaroos were about to come into oestrus, were in oestrus or had recently been in oestrus. Only 19% of a sample taken in a comparable locality were at oestrous stages during a season of normal rainfall. After rainfall kangaroos which had failed to exhibit post-partum oestrus during the preceding drought came into oestrus and ovulated while suckling pouch young up to 163 days old. Ovulation after rainfall did not occur in kangaroos with a functional corpus luteum or a resting corpus luteum of lactation in one or other ovary. This suggests that the corpus luteum of the red kangaroo exerts an ovulation-inhibiting effect and that ovulation in this species, unlike in some other marsupials, is not inhibited by suckling. Removal of corpora lutea of lactation in suckling animals and of functional corpora lutea in non-suckling animals was followed by precocious return to oestrus. There was, however, evidence that non-suckling animals returned to oestrus following ablation of the corpus luteum sooner than did suckling animals.

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PAMELA ARMAN, R. N. B. KAY, E. D. GOODALL and G. A. M. SHARMAN

Summary.

The gross anatomy of the mammary gland of the red deer is described. A total of 102 milk samples was obtained from six deer (four during a complete lactation). These contained an average of 21·1 % total solids (8·5% fat) in early lactation, rising to 27·1% (13·1% fat) in late lactation.

Milk yields were measured by the calf-weighing technique. In well-fed hinds, peak yields of 1400 to 2000 g/day were reached early in lactation. One hind on a restricted food intake gave a maximum of 970 g/day. Lactation continued for 190 to over 280 days. Total yields for the first 150 days were estimated to be 140 to 180 kg in well-fed hinds and 65 kg in the underfed hind.

The feed intakes of the hinds rose during late pregnancy, and in early lactation rose again markedly, to a level about 2·4 to 2·6 times the maintenance requirement of non-breeding animals.

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G. B. SHARMAN, E. S. ROBINSON, SHIRLEY M. WALTON and PATRICIA J. BERGER

Summary.

Two intersexual tammar wallabies (Macropus eugenii), one intersexual euro (Macropus robustus) and one intersexual brush possum (Trichosurus vulpecula) were studied.

One tammar had 17 chromosomes instead of the 16 characteristic of the species. There were 14 autosomes and two X and one Y sex chromosomes (XXY intersex). The animal was of female body phenotype (weight basis) and had a pouch containing four everted and well-developed teats with underlying mammary tissue. Undescended non-functional testes were present, one of which was distinctly abnormal. The accessory reproductive structures (apart from the pouch and mammary glands) were of the male type and the penis was well developed.

In the second tammar, dividing cells resembling spermatogonia in one gonad had 14 autosomes and one X chromosome (XO intersex). This animal was of female body phenotype and had a pouch containing two very small teats on one side, with underlying rudimentary mammary tissue. A small scrotum was present. The gonads were nonfunctional, undescended ovo-testes. Both gonads had tissue resembling the interstitial tissue of the normal ovary, and structures containing cells resembling undifferentiated spermatogonia. The accessory reproductive structures were essentially of the female type.

The intersexual euro and the intersexual brush possum (XY intersexes) had well developed pouches containing rudimentary mammae but on dissection were found to have normal male reproductive systems, the testes being within the body cavity. These had small testicular tubules and a greater than normal quantity of interstitial tissue. There were no meiotic stages of spermatogenesis.

It is concluded that the Y chromosome is strongly male-determining and that there is no obvious correlation between karyotype and occurrence of pouch and mammary tissue in marsupials.