ABSTRACT
Aphrodite aculeata L., the sea mouse, is generally dredged from muddy bottoms, where it burrows head-first into the mud. Usually only the anal extremity, which is very mobile and often held in an upturned position, remains uncovered.
The ventral body surface, between the segments, shows more or less well-defined grooves. It is particularly in these grooves that the water is seen to flow in a lateral direction.
In an animal covered with sand, the dorsal felt follows the movements of the scales very closely. In specimens lying free on the substratum the felt seems to move to a smaller extent.
The felt is formed by threads which issue from the parapodia, and exhibits small lateral intersegmental openings.
Nierstrasz & Hirsch (1922, p. 41) described an anterior, inspiratory opening in the felt. This is erroneous; such an opening is only present in damaged specimens.
According to Fordham (1925, p. 39) the first sign of expiration is an elevation of the elytra to their maximum extent. In my opinion this “elevation” is probably brought about, not by the extension of the elytrophores but by the elevation of the dorsum, which may occur somewhat prior to the depression of the scales.
