Neither here nor elsewhere are cilia found at any period of development.
Some, however, are wanderers, either swimming actively with the aid of cilia, or floating inertly as the result of a specific weight closely approaching that of the medium.
The epidermis has lost its connected epithelial character and its cilia, and the isolated cells have become sunk inwards retaining their S t- FIG.
By the aid of these cilia the larva swims actively, but owing to its minute size it covers very little distance, and this probably accounts for the fact that where brachiopods occur there are, as a rule, a good many in one spot.
In Nucula delphinodonta the test is uniformly covered with short cilia, and there is no flagellum.