Stages in the development of the larva of Terebratulina septentrionalis.... The youngest larva has two segments, a third then appears, the larva then fixes itself, and the second segment folds over the first and develops bristles round its edge.
Brood-pouch of Thecidium mediterraneum. Part of the wall of the pouch has been removed to show the clusters of larvae.. 1. Mouth, overhung by lip.; 2. One of the two median tentacles which are enlarged and modified to bear the larvae.
Figures illustrating the tubes in which Lingula anatifera lives. The upper figure is a view of the trilobed opening of the tube. The lower figure shows the tube in the sand laid open and the animal exposed. The dotted line indicates the position of the body when retrcted. The darker portion is the tube of sand agglutinated by the secretion of the stalk..