Morphological observations on the diapausing blastocyst of some macropodid marsupials

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.