The female has four mammary glands. Two on the upper chest and two on the lower abdomen, just the right number for the quadruplets that are born each time. The four young, always of the same sex, come from a single fertilized egg. The embryo starts as a single individual; however, through a process of bisection, followed by a second sub-division, four clone-like embryos are formed. Each is enclosed in its own membrane sac.