 An egg weighs  and is about long.While hatching, the baby echidna opens the leather shell with a reptile-like egg tooth.Hatching takes place after 10 days of gestation; the young echidna, called a puggle, born larval and fetus-like, then sucks milk from the pores of the two milk patches (monotremes have no nipples) and remains in the pouch for 45 to 55 days, at which time it starts to develop spines.