Summary. Diapausing blastocysts from the uteri of females of 11 macropodid species were fixed, torn, flattened and stained for examination of the protoderm. The protoderm remained undifferentiated and unilaminar throughout diapause. The number of cells in the protoderm did not vary with age in Macropus rufus or M. eugenii. Protoderm cell number decreased slightly with age in M. rufogriseus banksianus and appeared to decrease in Potorous tridactylus. The diameter of the shell did not change appreciably with age, and the sizes of the blastocysts of different species were similar.
MEREDITH J. SMITH and GILLIAN K. GODFREY
Injection of hcg into mature, female S. crassicaudata induced ovulation in three of six animals, whereas injection of pmsg or of pmsg followed after 48 hr by hcg induced ovulation in all of seventeen females. Seven mated but none littered.
Ten adult females were injected with pmsg and hcg at the end of an induced oestrous cycle, when the corpora lutea were degenerate. Six mated but none littered. Of eight young females injected with pmsg and hcg, four mated but again none littered. All ova recovered after induced ovulation were unfertilized.
The number of ova released at induced ovulation was higher than in untreated animals and many unruptured follicles became luteinized. Ova were retained in the oviducts for longer than normal.