SB 4.29.2
narada uvaca
purusam purañjanam vidyad
yad vyanakty atmanah puram
eka-dvi-tri-catus-padam
bahu-padam apadakam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The great sage Narada Muni continued: You must understand that Purañjana, the living entity, transmigrates according to his own work into different types of bodies, which may be one-legged, two-legged, three-legged, four-legged, many-legged or simply legless. Transmigrating into these various types of bodies, the living entity, as the so-called enjoyer, is known as Purañjana.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
How the spirit soul transmigrates from one type of body to another is nicely described here. The word eka-pada, “one-legged,” refers to ghosts, for it is said that ghosts walk on one leg. The word dvi-pada, meaning “biped,” refers to human beings. When he is old and invalid, the human being is supposed to be a triped, or three-legged, because he walks with the help of a stick or some kind of cane. Of course, the word catus-pada refers to quadrupeds, or animals. The word bahu-pada refers to those creatures who have more than four legs. There are many insects, such as the centipede, and also many aquatic animals that have many legs. The word apadaka, meaning “without legs,” refers to serpents. The name Purañjana indicates one who enjoys possessing different types of bodies. His mentality for enjoyment in the material world is accommodated by different types of bodies.