Q. What do you mean by Echinodermata?
You will recall that Pliylum Echinodermata includes spiny skinned animals which are exclusively marine (Gr, echinus : spiny; derma: skin). They have the following characters which are not found in animals belonging to any other phylum:
i) Bilaterally symmetrical but radially symmetrical adults. Thus they exihibit secondarily pentamerous, radial symmetry found in adults.
ii) A skeleton made of calcareous plates or ossicles ,bearing projecting spines.
iii) Small pincer-like bodies present among plants called pedicellarise.
iv) Organs called "tube feet" or podia responsible for locomotion.
You shall be able to see the above-mentioned features when you handle echiinoderms.
Echinoderms also possess certain unique features which can be seen after dissecting
The animals. These features are:
(i) a system of coelomic channels forming a water vascular system with external tubular projections used in feeding and locomotion.
(ii) a blood lacunar system called the haemal system.