EXPLANATION OF FIGURES
[Fig. 1]. Diagram of the ganglia of Nucula castrensis, reconstructed from serial sections. The probable position of the connectives is shown and the proportionate distances between ganglia are given. The upper ganglion is the cerebro-pleural with large nerves leading off from the ganglion which is itself lobed into four chief lobes. The pedal ganglion is next. In section the pedal ganglion at one place seems to be made up of four parts which may correspond to four connectives from the cerebro-pleural although only one pair of connectives was clearly determined. The visceral ganglion is connected with the pedal below. ×70.
[Fig. 2]. Cross section of cerebro-pleural ganglion. On the right side one of the lateral ganglia is shown. The one of the other side does not show because the section is not straight across. The dorsal side is up. ×300.
[Fig. 3]. Section of the pedal mass of Nucula, through the center. The dorsal side is up. ×300.
[Fig. 4]. Left side of the visceral mass of Nucula. Dorsal side up. ×300.
[Fig. 5]. Nerve cells from the central nervous system of Nucula. ×450.
[Fig. 6]. Section through the body of Nucula showing the position of the cerebro-pleural ganglion cut through the center. Dorsal side up. The cellular portion of the ganglion is black. ×70.
[Fig. 7]. Section through the body of Nucula at the level of the visceral nerves which are shown on either side of the section. The area of nerve cells is shown in black. ×70.
[Fig. 8]. Reconstruction from serial sections of the cerebro-pleural mass nerves and connectives of Malletia faba. The drawing is a ventral view, the cephalic side is at the top. ×70.
[Fig. 9]. Reconstruction of pedal ganglion of Malletia from the ventral side. Cephalic side at the top. ×70.