Litera-significations. 



Where not stated otherwise, tlie liter;i-signilicatiuiis are tlie same in all the Plates 



mu. — Mouth. 

 an. — Cloacal aperture. 

 S.O. — Segmental j^landuloiis sacks, 

 t — Male genital a]ierture (Penis). 

 gf — Sub-ectodermal testes. 

 in. — Tentacidar nerves. 

 t.r — Tentacular nerve-ring. 



Ctrl' ctir, cm'" — Nerves connecting the tentacu- 

 lar nerve-ring with the oesophageal ring. 

 O.r. — Oesophageal ting. 



O.cm. — Oesophageal commissures. 



O.n. — Oesophageal nerves. 



l.cm. — Longitudinal commissures. 



i.n. — Intermediate nerve. 



n. — Nerves. 



n.st. — Large nerves. 



n.c. — Ganglionic cells. 



ffi: — Groups of ganglionic cells. 



6. S'. — Ventral nerve-cord. 



f.g. — Parapodial ganglia. 



n.sk. — Neurilemma-sheath. 



OV.d. — Oviducts. 



t. — Testes. 



tm. — Intestinal hranches. 



cl. — Cloacal canal. 



mv. — Stomach. 



m. — Muscles. 



h. — Hooks. 



r.h. — Reserve hooks. 



h.k. — Hook-glands. 



Figures. 



Fig. I, 2. M. graffi, n. sp. Dorsal and ventral aspects; magnified about i; times. (Cam.-luc.) 

 » 3. M. giganteim, n. sp. Magnified about 10 times. (Cam.-luc.) 



, 4 Do. Anterior portion, dorsal aspect, proboscis extended; magnified 15 times. (Cain.-luc.) 



« 5. M. gigas, Liitken. Complemental male. Ventral aspect ; magnified 15 times. (Cam.-luc.) 



» 6,7. M. carpenter i, Graff. Dorsal and ventral aspects; magnified 7V2 times. (Cam.-luc. and reduced to half size.) 

 y. 8. M. gigantewn, n. sp. (Zeiss AA. Oc. i. Osmic acid. Hæmatoxylin ').) Ideal horizontal .section through left-hand half, 

 representing the distribution of the nervous system. The illustration is obtained by means of a series of horizontal sections, 

 and is, parti}', drawn under the Camera-lucida. At the base of the proboscis, the transsected oesophageal ring {or.), with 

 circumjacent groups of cells {gr.), is seen. At the anterior end of the muscular bulb, the transsected tentacular 

 nerve-ring [tr.), with the pertaining tentacular nerves {tn.), oesophageal nerves etc. and nerves {cm.) connecting it 

 with the oesophageal ring, is seen. In the centre of the section, the \entral nerve-cord, with its two longitud- 

 inal commissures {i.ctn.), between which ganglionic cells and the intermediate nerve are situated, is seen. 11 pairs 

 of nerves are seen to issue — 6 pairs of fine ones (■».' — «.«) and 5 pairs of large ones — from the latter, branches run to the 

 parapodia and their muscles, also to the parapodial ganglia {f.g.) and to some muscles in the body (c), and to 

 the cirri and margin of the bod}-. At each cirrus, the branches form a complex ramification (a.) sending a bundle 

 of nerves into the cirrus. /. Branchlet of the medial nerve-branch, anastomozing with a branchlet from the ulterior posterior 

 nerve-branch. d. Parapodial nerve-branch dividing into two branchlets, the posterior one of which is the largest 

 and corresponds to the anterior branch at the three first pairs of parapodia. On the inner side of the hooks and their 

 surrounding muscles at each parapodium, the inner branch (7(. h.) of the hook-glands is seen transsected. p Trans- 

 sected depression in the ventrum at the outer side of each parapodium. Ovd. A latero-ventral oviduct opening into 

 the cloacal canal {cl.). Ovd. (at the lower margin of the figure) Transsected dorsal oviduct, et., et, et. Sub-ecto- 

 dermal testes, principally situated in the margin of the bod}-. 

 » 9. Schematic representation of the structure of the oesophageal ring and proboscideal nervous system in 

 M. giganteim, n. sp. Dorsal aspect. The anterior part of the ventral nerve-cord is seen, from which the oesophageal com- 

 missures {o.cm.) forming the oesophageal ring issue; a few ganglionic cells occur in two places, one on each side 

 (a.) within its neurilemma-sheath. The mesial part {h.), on the dorsal side of the ring, is very thin and flat. The 

 ganglionic cells occurring between the oesophageal ring and the tentacular [nerve-ring are, to avoid confusion, not 

 illustrated in the figure, gr. Groups of cells, situated at the back of the oesophageal ring on the dorsal side, s.c 

 The ventral portion of the cellular ring surrounding the proboscis. -«". A nerve, proceeding towards the ventral side of 

 the proboscis, n. A nerve directed forwards, cm.', cm.", cm.'". The three nerves connecting the oesophageal-ring 



with the tentacular nerve-ring {t.r.) o.n. 



One of the 4 oesophageal nerves. 2) n.s. Nervus sympathicus. n.st., n.st.^. 



10. 



II. 



Respectively, the first and second of the large nerves issuing from the ventral cord, n'., n'-. Respectivel}-, the first 

 and second of the fine nerves, Ganglionic cells are seen situated in the ventral cord, between the roots of the 

 nerves, as well as (c.) between the longitudinal commissures {l.cm.) and the intermediate nerve {in.). 

 Schematic representation of the tentacular nerve-ring viewed from the anterior side, o.n., o.n. and the two cor- 

 responding nerves of the other side, are the roots of the 4 oesophageal nerves, cm., cm. are the roots of the 

 nerves connecting the oesophageal ring, n., n. Fine nerves passing to the walls of the proboscideal canal. 

 M. graffi, n. sp. (Zeiss AA, Oc. i. Cam.-luc.) Transverse section through the posterior part of the body, at the 

 point where the lateral oviducts {ov.d.), issue from the dorsal oviduct {ov.d '). The lateral oviducts are, owing to 

 their meandering course, transsected in several places. «.', n.' The posterioriy directed 5th pair of large nerves. 

 n., n. The posterior 6th pair of fine nerves a. A small portion of the body cavity, in which ova are situated. 

 tm. A transsected dorsal branch of the intestine. 



I) Where, in the description of the figures, «osmic acid, hæmatoxyliu« is stated the specimens, preserved in .alcohol, «ere immersed for 6 to 

 12 hours in a solution of i "/„ osmic acid, then washed out, stained with hæmatoxyliu and imbedded. The sections were usually treated with a weak 

 solution of eosiu in a mixture of turpentine and a little abs. alcohol. Where «liora.K-c.armine, picric acid" is stated the specimens were stained in toto with 

 borax-carmine; and the sections were treated with a solution of picric acid in a mixture of turpentine and abs. alcohol. 



') I am not certain that these nerves are connected with the oesophageal ring as indicated at d. 



