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May 15, 1873]
NATURE
5i
NOTES PROM THE "CHALLENGER» * * II.

ON Sunday, March 2, we saw the first patches of gulf-weed drifting past the ship, and flying-fish were abundant. Our position at noon was lat. 220 30' N., long. 420 6' W., Sombrero Island distant 1,224 miles. At night the phosphorescence of the sea was particularly brilliant, the surface scintillating with bright flashes from the small crustaceans, while large cylinders and globes of lambent light, proceeding probably from Pyrosoma and some of the Medusae, glowed out and slowly disappeared in the wake of the vessel at a depth of a few feet.

The next morning we sounded at 7 A.M. in 2,025 fathoms with No. 1 line, the "Hydra" machine and 3 cwt., a slip water-bottle, and one thermometer ; a stopcock water-bottle was bent on at 925 fathoms from the bottom. The corrected bottom temperature was i°'9 G, the temperature of the surface being 220,8 C. During the morning the naturalists were out in a boat with the
towing-net, and they brought back a number of fine examples of Porpita, several of Glaucus atlanticus, some shells of Spirula bearing groups of small stalked cirripeds, and many large radiolarians. One of the Spirula shells was covered with a beautiful stalked infusorian.

We proceeded in the evening under all plain sail. The soundings on the chart in advance of us seemed to indicate an extensive rise, with a depth of water averaging not much more than 1,700 fathoms, and it was determined to dredge again on the following day.

On the morning of March 4 we sounded in lat. 210 38' N., long. 440 39' W., in 1,900 fathoms, with No. 1 line, the " Hydra" and 3 cwt., the slip water-drop, and a thermometer. The bottom was grey ooze, as on the day before, and the bottom temperature i0#9 C. The dredge was put over at 8 A.M. It was intended to attach a " Hydra " tube with disengaging weight a little below the bottom of the dredge ; the weight slipped, however, close to the surface, and the dredge was lowered in the ordinary
way with cwt. 500 fathoms in advance. The dredge came up about 4 o'clock with a small quantity of ooze containing some red clay, a large proportion of calcareous debris, and many foraminifera, chiefly Otbulina and Rotalia.

Warped in the hempen tangle there was a fine specimen of a handsome decapod crustacean, having all the principal characters of the family Astacidae, but differing from all the typical decapods in the total absence of eye-stalks and eyes. Dr. v. Willemoes-Suhm has given this interesting deep-sea form such a preliminary examination as is possible in the absence of books of reference. I quote from his notes. Deidamia leptodactyla, n.g. and sp. (Fig. 2). The specimen, which is a male, is 120 mm. in total length and 33 mm. in width across the base of the cepftalo-thorax, which is 60 mm. in length. Three rows of spines, one in the middle line and one on each side, run along the cephalo-thorax, which is divided by a transverse sulcus into an anterior and a posterior part, the former occupied by a central gastric and lateral hepatic regions, and the patter by a central cardiac and * Continued fro.n p 30.
Fig. a.—Deidamia lep todactyla, R. v. S. -
latent bronchial regions. The abdomen, which consists as usual of seven segments, has the central series of spines of the cephalo-thorax continued along the middle line. The sixth segment bears the caudal appendages, and in the seventh, the telson, we find the excretory opening. The lateral borders of the body, and all the appendages with the exception of the first pair of ambulatory legs, are edged with a close and very beautiful fringe of a whitish-yellow colour.

There are two pairs, the normal number, of antennae, then come mandibles, then maxillae; three pairs of maxillipeds, five pairs of ambulatory legs, and five pairs of swimmerets. As most of the appendages differ from those usually met with in the Astacidae only in detail, I need here only mention that the anterior antennae have two pairs of flagella, one of which is very long, longer than the external flagellum of the external pair.

The form of the first pair of ambulatory legs is singularly elegant. They are 155 mm. in length—considerably longer than the body; they are very slender, and end in a pair of very slender denticulated chelae, with a close,

 

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52
NATURE
[.May 15, 1873
velvet-like line of hairs along their inner edges. The rest of the apibulatory legs are much shorter, and all bear chelze, a character which will demand a certain relaxation of the diagnosis of the Astacidae if Deidamia is to be placed in that family.

The specimen captured being a male, the first pair of swimmerets are somewhat modified. The four other pairs of swimmerets, which are 33 mm. in length, bear each two narrow swimming processes richly fringed with hair, and a short flagellum.

The absence of eyes in many deep-sea animals and their full development in others is very remarkable. I have mentioned ("The Depths of the Sea," p. 176), the case of one of the stalk-eyed crustaceans, Ethusa granulata, in which well-developed eyes are present in examples from shallow water. In deeper water, from 110 to 370 fathoms, eye-stalks are present, but the animal is apparently blind, the eyes being replaced by rounded calcareous terminations to the stalks. In examples from 500 to 700 fathoms in another locality, the eye-stalks have lost their special character, have become fixed, and their terminations combine into a strong pointed rostrum. In this case we have a gradual modification, depending apparently upon ihe gradual diminution and final disappearance of solar light. On the other hand, Munida, from equal depths, has its eyes unusually developed and appa-rently of great delicacy. Is it possible that in certain cases, as the sun's light diminishes, the power of vision becomes more acute, while at length the eye becomes susceptible of the stimulus of the fainter light of phosphorescence? The absence of eyes is not unknown among . the Astacidce. Astacus pellucidusy from the Mammoth Cave, is blind, and from the same cause—the absence of light; but morphologically the eyes are not entirely wanting, for two small abortive eye-stalks still remain in the position in which eyes are developed in all normal decapods. In Deidamia no trace whatever remains either of the eyes of sight or of their pedicels.

On Thursday the 6th we sounded in 2,325 fathoms, sending down a thermometer and the slip water-bottle.. The temperature registered was i°7 C., and the specific gravity of the sample of water was 1-02470 at 210 C., that of the surface water being 1-02556, at 23°'3 C.

A good deal of gulf-weed drifted past during the day, and a boat was sent out to collect some. About half a dozen closely twined bundles were procured, and on examining them it was found that the bundle was bound together by strings of the viscid secretion of Antennarius marmoratiiSy and formed a nest containing the eggs of the fish. Several young examples of this grotesque little animal have been from time to time brought in among the gulf-weed ; also many crustaceans, several of the nudibranchiate mollusca characteristic of the gulf-weed fauna, such as Scillaa pelagica p., and many planarians.

The dredge came up at 4.15 p.m. with a small quantity of red mud, in which we detected only one single but perfectly fresh valve of a small lamelli-branchiate mollusk. In the mud there were also some sharks' teeth of at least two genera, and a number of very peculiar black oval bodies about an inch long, with the surface irregularly reticulated, and within; the reticulates closely and/symmetrically granulated the whole appearance singularly like that of the phosphatic concretions which are so abundant in the greensand and trias. My first impression was that both the teeth and the concretions were drifted fossils, but on handing over a portion of one of the latter to Mr. Buchanan for examination, he found that it consisted of'almost pure peroxide of manganese.

The character both of the exterior and interior of the nodule strcngly recalled the black base of the coral which we dredged in 1,530 fathoms on the 18th of February; and on ^oing into the matter, Mr. Buchanan found not only that the base of the coral retaining its external organic form had the composition of a lump of pyrolusite,
but that the glossy black film covering the stem and branches of the coral gave also the reaction of manganese. There seemed to be little doubt that it was a case of slow substitution, for the mass of peroxide of manganese forming the root showed on fracture in some places the concentric layers and intimate structure of the original coral. The coral, where it was unaltered, had the ordinary composition, consisting chiefly of calcic carbonate. Whether the nodules dredged on March 7th are pieces of rolled coral, the ornament on their surface being due to an imperfect crystallisation of the surface layer of the peroxide of manganese, or whether they form another case of pseudomorphy, the peroxide of manganese replacing some other organism, we have not the means of determining. The whole question is a very singular oi\e.

Some of our party, using the towing-net and collecting gulf-weed on the surface from a boat, brought in a number of things beautiful in their form and brilliancy of colouring, and many of them strangely interesting for the way in which their glassy transparency exposed the working of the most subtle parts of their internal machinery ; and these gave employment to the microscopists in the dearth of returns from the dredge. Our position was now lat. 190 57' N., long. 530 26'; Sombrero distant 558 miles.

Sunday was a lovely day.—The breeze had fallen off-

somewhat, and the force was now only from 2 to 3. The sky and sea were gloriously blue, with here and there a soft grey tress on the sky, and a gleaming white curl on the sea. A pretty little Spanish brigantine, bright with green paint and white sails,-ahd the merry, dusky faces of three or four Spanish girls, came in the morning within speaking distance and got her longitude. She had been passing and repassing us for a couple of days, wondering doubtless at the irrelevancy of our movements, shortening sail, and stopping every now and then in mid ocean with a fine breeze in our favour. On Monday morning we perted from our gay little companion. We stopped again to dredge, and she got far before us, and we saw with some regret first her green hull and then her white sails pass down over the edge of the world.

The sounding on Monday the 10th gave 2,675 fathoms, with a bottom of the same red clay with very little calcareous matter. The bottom temperature was i0,6 C., that of the surface being 23°'3 C. We had been struck for some time past. with the. singular absence of the higher forms of life. Not a bird was to be seen from morning to night. A few kittiwakes {Lams tridactylus) followed the ship for the first few days after we left Tene-rifie, but even these had disappeared. A single petrel (Thaiassidroma pelagica) was seen one day from one of the boats on a towing-net excursion, but we had not seen one of the southern sea-birds. For the last day or two some of the larger sea-mammals and fishes had been visible. A large grampus (Orca gladiator) had been moving round the ship and apparently keeping up with it. Some sharks hung about, seeking what they might devour, but we had not yet succeeded in catching ♦ any of them. Lovely dolphins (Coryphcena hippnrus) passed in their varying irridescent colouring from the shadow of the ship into the sunshine, and glided about like living patches of rainbow. Flying-fish became more abundant, evidently falling a prey to the dolphins, which are readily deceived by a rude imitation of one of them, a white spinning bait, when the ship is going rapidly through the water.

On Tuesday the nth we pursued our course during the forenoon at the rate oT from six to seven knots, with a light breeze, force 3 to 4. The dredge-line was veered to over 4,000 fathoms, nearly 5 statute miles. The dredge came up at about half-past five o'clock, full of red mud of the same character as that brought up by the sounding machine. Entangled about the mouth of the dredge and embedded in the mud were many long cases of a tube-