Supra neural gland is the excretory organ of Herdmania.

Herdmania, also known as sea squirt or tunicate, is a marine invertebrate belonging to the phylum Chordata. It is a filter-feeding organism that lives attached to a substrate in shallow coastal waters. Like other members of the phylum Chordata, Herdmania possesses certain characteristics such as a notochord, a dorsal hollow nerve cord, and pharyngeal gill slits during its larval stage.

The excretory system in Herdmania is responsible for eliminating metabolic waste products from its body. The excretory organ in Herdmania is known as the supra neural gland.

Explanation of options:

a) Protonephridia: Protonephridia are excretory structures found in flatworms, such as planarians. They consist of flame cells that remove metabolic waste from the body. However, Herdmania does not have protonephridia as its excretory organ.

b) Supra neural gland: The supra neural gland is the correct answer. It is a glandular structure located above the neural ganglion (nerve center) in the body of Herdmania. It is responsible for excretion and osmoregulation. The supra neural gland helps in removing nitrogenous waste products, such as ammonia, from the body.

c) Solenocytes: Solenocytes are excretory cells found in certain invertebrates, such as flatworms and rotifers. They are responsible for excretion and osmoregulation by removing waste products and regulating the balance of water and ions in the body. However, Herdmania does not have solenocytes as its excretory organ.

d) Metanephridia: Metanephridia are excretory organs found in segmented worms, such as earthworms. They consist of a network of tubules that collect waste products from coelomic fluid and eliminate them through pores called nephridiopores. However, Herdmania does not have metanephridia as its excretory organ.

In conclusion, the correct excretory organ of Herdmania is the supra neural gland, which is responsible for excretion and osmoregulation in this marine invertebrate.