PLATE XV. 



Fig. 



1. Transverse section somewhat behind that shown in Plate XI, fig. 1. The instrument has 



passed obliquely across the body so as to cut the ganglia at different distances from the 

 front. On the right only the tip of the superior lobe remains, while the commencement 

 of the great nerve-trunk — in full bulk — is cut beneath. X 90 diam. 



2. Snout and anterior region of A. pulcher. g,g, glandular masses. X 55 diam. 



3. Arrangement of the circulatory and nervous systems in A. lactifloreus (a small specimen). 



X about 40 diam. 



4. Portion of the head of the same species considerably flattened. X 210 diam. 



5. Head of Nernertes Neesii. X about 60 diam. 



6. Nerve-cells from a cephalic ganglion of A. lactifloreus. X 400 diam. 



