A survey of animal kingdom presents a variety of excretory structures. In most of the invertebrates, these structures are simple tubular forms whereas vertebrates have complex tubular organs called kidneys. Some of these structures are mentioned here.

(i) Protonephridia or flame cells are the excretory structures in Platyhelminthes.

(ii) Planaria and Amphioxus have protonephridia is a excretory structures.

(iii) Nephridia are the tubular excretory structures of earthworms and other annelids.

(iv) Nephridia help to remove nitrogenous wastes and maintain a fluid and ionic balance

(v) Malphighian tubules are the excretory structures of most of the insects and molluscs including cockroaches.

(vi) Antennal glands or green glands perform the excretory function in crustaceans like prawns.

Which of the following statements are correct?