The larvae are elongate and worm-like, with short legs but often with hard strong cuticle.
The footless larvae are elongate, worm-like and very active; they feed upon almost any kind of waste animal matter, and when full-grown form a silken cocoon.
The skeleton is cartilaginous, and the skull is remarkable for the very elongate suspensorium of the lower jaw; the tail remains in the notochordal condition, no cartilages being formed in this organ, which is destined to disappear with the gills.
The larvae are remarkable for their small head, very broad thorax, with reduced legs, and narrow elongate abdomen.
What characterizes a tadpole is the conjoined globular head and body, so formed that it is practically impossible to discern the limit between the two, sharply set off from the more or less elongate compressed tail which is the organ of propulsion.