in Anatomy. All fetuses are wrapped up in at least two coats or membranes; most of them have a third, called allantoides, or urinary.

Some, as the dog, cat, hare, &c. have a fourth, which has two blood-vessels, viz. a vein and an artery, called omphalo-mesenteries, because passing along the string to the navel, and terminating in the mesentery.