Lays eggs and hatches them in an underground tunnel much like a bird. Eggs hatch in 10-14 days. Young live entirely on milk for 3 4 mos. The mother has no nipples; milk extrudes from 100-150 separate gland tubes that open at the base of a stiff hair. The glands are paired. Secretory tubes have 2 cell layers, an inner secretory layer and an outer contractile layer. There is no internal storage of milk. Milk is secreted onto the hairs and is lapped off by the young.

Sometimes called the echidna or spiny anteater. Lays eggs which are transferred to a pouch. Mammary glands are located in the pouch. She has no nipples. Milk oozes from several ducts into indentations in the skin. There is no storage reservoir. There is a milk ejection response.