Body is divided into body proper and test.
Free end of the body proper has 2 short cylindrical projections called branchial and atrial siphons. Atrial siphon is larger.
The aperture to the siphons have four distinct lobes formed by the test.
Foot is entirely formed by test.
The foot serves functions of attachment and anchorage, and also as a balancer when the body is detached from the substrate.
Test is almost transparent in young stage but becomes opaque in the adult due to thickening.
Test forms a platform for organisms like algae, hydroids, anemones, molluscs, barnacles.
Composed of clear gelatinous matrix in which cells are embedded, corpuscles of various types, interlacing fibrils, branching blood vessels, calcareous spicules.
Gelatinous matrix is made of a polysaccharide Tunicine.
The mantle is suspended inside the test (which it secretes) and remains attached only at branchial and atrial apertures
Mantle encloses the Atrium, which is a large water filled cavity.
All the soft body parts are enclosed by the mantle.
Gonads
2 large gonads embedded in the mantle and bulging into atrial cavity.
Right gonad is situated parallel and dorsal to pericardium.
Left gonad lies within the intestinal loop.
Each adult gonad is an elongated, lobulated, hermaphrodite gland.
10-25 oval lobes arranged in 2 rows on either side of a central axis.
Each lobe is made up of a larger brick red testicular region, and a smaller inner ovary region. Each lobe is thus an ova-testis.
Each gonad has a sperm duct and an oviduct (oviduct is
wider).