They contain a well developed muscular system. The digestive system is adapted to digest whole prey, swallowed by the organism. Two kidney's rid the body of nitrogenous waste. The cloaca is a sac that collects discharge from the large intestine, urinary bladder, and gonads before it is eliminated from the body. Their brain is well developed and is attached to a dorsal nerve cord.
Most amphibians contain three eye lids.
Two are normal and one is transparent. These are the first animals to possess a pressure releasing canal called the Eustachian tube . The tube connects the mouth cavity with the tympanic membrane . This order contains amphibians without legs. Examples of this order are the caecilians.