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 MARINE ZOOLOGY 3. Sagartia viduata (O. F. Mailer). This is common in the Crouch at Burn- ham on the south shore, but seen only when the tide is low. It can be killed in an ex- panded state by using menthol. 4. Sagartia troglodytes. What are probably young or somewhat small individuals of this species are common in the Orwell, a short distance outside Essex. 5. Ttalia crassicornis (O. F. Mtlllcr). I have occasionally caught this in the Crouch when trawling, and it is often dredged in the more open sea. I have collected a fair number of specimens at low water on both the east and west shores of the Colne near Brightlingsea. In 1901 it was very abundant on the shore off Harwich, near the level of extreme low water. 6. Halcampa chrysanthellum (Gosse). Found in sandy gravel near the mouth of the Colne, but the colour of the disk differs somewhat from the Cornish specimens de- scribed by Gosse. Though Actinia mesembryanthemum is so common on the coast of Kent, I have never seen one in Essex. IV. NEMERTINEA 1. Lineui obscurus, Desor. The only place where I have found this is in the mud at Mistley. 2. Amphiporus lactifloreus, Johnston. I have found only one specimen, which was obtained in the Orwell a short distance out- side Essex. V. NEMATODA (?) Nectontma (?) I have never seen more than one specimen, which was caught wriggling about at the sur- face in the Stour off Harwich. It is 11$ inches long and ^ inch thick and full of eggs, and is almost certainly a fish parasite which had escaped from its host when mature. VI. ANNELIDA I. POLYCH^ETA I. Aphrodita aculeata (Linn.). This used to be fairly common in the Stour off Harwich, but lately I have not obtained it there. It is much more common in the Wallet near the Gunfleet bank. 2. Lepidonotus squamatus, Linn. This occurs commonly in most parts of the district. It is often found in the tubes of Amphitrite Johnstons. 3. Nereis diver sicoler, Mull. Very abundant in the mud banks of St. Osyth's creek and found in most other Essex estuaries, though comparatively rare in the Crouch. In some places it is much coloured by a fugitive green pigment, and in others coloured red by the great amount of hemo- globin which is comparatively absent in others. In some places almost at high water mark and up the estuaries far from the sea it is abundant to the exclusion of other similar animals. 4. Nereis cultrifera (Grube). Common in particular places in sandy mud near low water mark at the mouth of the Colne and off Harwich. 5. Nereis pt/agica, Linn. All the specimens I have procured were dredged outside Harwich harbour, where it occurred amongst the sandy tubes built by Sabellaria spinulosa. 6. Nereis dumerilii y Aud. & M. Edw. Readily distinguished from the three other species by having very long tentacular cirri. I have always found it in tubes built amongst alga. When kept in a small aquarium it built a semi-transparent tube open at both ends and came out and ate Ulva and returned to its tube. It laid very many eggs without passing into the Hettranereis condition. What I believe was the same species passed into that condition in my larger aquarium, but they may have been males. Though I have lived in the Orwell and Stour for a total period of between one and two years I seldom if ever saw Heteronereis except in the early morning of July 1 6, 1898, when males of about 2 inches long were swimming on the sur- face in Harwich harbour in such numbers that I estimated them at something like a million. When dried and mounted in Canada balsam this species differs from all the others in turning deep brown, but this does not hap- pen in the case of the male Heteronereis. 7. Nephthys hambergii (Cuvier). Common in the more or less sandy mud exposed at low water in the Colne and near Harwich but much rarer near Burnham. It varies considerably in colour owing to the greater or less amount of hzmoglobin and of a brown pigment. 79