Part 75

Fig. 1 _a_, Basal membrane, with the cementing apparatus, of _Coronula balænaris_; a small portion of the parietal membrane, _p p p_, which coats the folded shelly walls, is left adherent to the basal membrane. _b_, the circumferential slip (shaded more darkly than the rest to catch the eye), separating the basal from the parietal membrane. _c′ c′_, slips of basal membrane, formed at each period of growth, and overlapping each other. _s s s s s s_, the six sutures in the walls, separating the six compartments, of which-- A is the basal margin of the rostrum, C C that of the lateral compartments, D D that of the carino-lateral compartments, and E that of the carina. _r_, _r_, rays or spokes of membrane, prolonged from the circumferential slip, and running under the trebly folded wall of each compartment, but here cut off; a similar ray should run under each line of suture (_s_). These rays, at their extremities, expand transversely; and the shape and length of the rays may be judged of from the basal outline of the folded walls given in Pl. 16, fig. 5. The two cement-ducts, proceeding from each cement-gland, debouch opposite the middle folds of the lateral (C C) and carino-lateral (D D) compartments. The layers of cement have been removed. N.B. There is one considerable error in this figure, the two main trunks, connecting the cement-glands, and meeting at the centre, have been represented as forming a straight line, but in fact they form a very open angle, as is correctly shown in fig. 1 _c_. 1 _b_, Diagram, representing a vertical section through a portion of the basal and parietal membranes, with the thickness of the membrane enormously exaggerated. _z z z_, layers of cement, which, if the section had been made in the line of the cement-ducts, would have been seen proceeding out of these ducts, as is represented at (_t_), where the section is supposed to have taken the above course. _c′ c′_, the slips of basal membrane. _b_, the circumferential slip; beneath this the coarsely dotted layer represents the cement, lately excreted, and before it has acquired its proper transparent structureless character, elsewhere represented by fine dots. _p_, membrane externally coating the walls of the shell. _t_, cement-ducts opening beneath the basal membrane. 1 _c_, The central portion of fig. 1 _a_, considerably magnified. _c′ c′_, slips of the basal membrane; but the shell, when these were formed, was so young that the walls had not acquired their folded structure; in the centre the prehensile antennæ of the pupa may be obscurely seen. _f_, the main cement-trunk, connecting the cement-glands. _h_, a cement-gland, from which two cement-ducts proceed. _a a_, cement-ducts (cut off), leading to opposite the middle fold of the carino-lateral compartment. _b b_, cement-ducts (cut off), leading to opposite the middle fold of the lateral compartment. _a′ b′_, a pair of cement-ducts, with their orifices opening on the under side of one of the slips of basal membrane (_c′_), at a point which once was opposite the middle of the carino-lateral and lateral compartments. The orifices of the other ducts, towards the centre, may be seen forming straight lines. 2, Cement-ducts and one cement-gland of _Chelonobia patula_, represented without the basal membrane, to which they adhere: _f_, _f_, main cement-trunk; _g_, enlarged portion; _h_, gland; _a_, _b_, the two ducts proceeding from this gland, and bifurcating several times before debouching on the under side of the basal membrane. Several other cement-ducts, proceeding from other glands, are represented just as they appeared under the microscope. 3, Cement-ducts and glands of _Tubicinella trachealis_, represented without the basal membrane to which they adhered: (_f_) (_f_), main cement-trunk, connecting the several glands; _h_, cement-gland; _a_, cement-duct, with a singular loop (_a′_) having two projections or rudimentary branches; _b_, spur or rudiment of a second cement-duct; _c_, third cement-duct. 4 _a_, Chain of cement-glands of _Balanus tintinnabulum_, _with all the ducts removed_, _excepting those proceeding from the last formed gland_, which latter correspond in age with the last-formed zone of the shelly basis; the whole of the basis having been removed by acid. _f_, main cement-trunk connecting the glands. _gh_, last-formed cement-gland. _k_, _t_, two cement-ducts, proceeding from a great common duct; one of these bifurcates at (_t_), and one branch joins at (_t′_) the corresponding branch from the corresponding gland. _i i i_, circumferential duct, into which the ducts _k_, _k_, _t_, _t_, _t′_ all enter. _i′ i′_, branches proceeding from the circumferential duct, which branch and sub-branch till they form a sheet (_z z_) of cement-tissue on the outside of the basis of the shell. 4 _b_, two cement-glands of _Bal. tintinnabulum_ (this figure, to match with 4 _a_, ought to have stood upside down), taken from near the centre of the basis, greatly enlarged; (_f f_), main trunk; (_g_), enlarged portion of the trunk; (_h_), gland; _k_, _t_, two cement-ducts proceeding from a common point, one of them (_t_) bifurcates, and gives off a rudimentary branch, _t′_; _m_, a spur, or rudimentary duct. The gland, _h_, has been pushed on one side, it ought to lie over the enlarged portion (_g_). There is a considerable difference between these two glands and that (_gh_) represented in fig. 4 _a_; the neck of the gland in the latter being elongated into a great common duct, and the spur or rudimentary duct (_m_) being absent.

PLATE 29.

CIRRI AND LARVÆ, FIRST STAGES.

Fig. 1, Sixth cirrus of _Balanus amphitrite_ (_var._ cirratus), showing the muscles. _a_, _b_, flexor and extensor muscles, moving the upper segment (_i_ to _k_) of the pedicel. _c_ and _d_, flexor and extensor muscles, apparently moving the lower segments of both rami, as a whole; the lower articulations in these rami being confluent. _e_ and _f_, flexor and extensor muscles extending up both rami (those only in the near ramus being figured) to their tips. _g_ _g_, flexors of the separate segments in both rami. _h_, basal articulation of lower segment of the pedicel. _i_, upper articulation of lower segment of the pedicel. _k_, upper articulation of upper segment of pedicel. 2, Fourth cirrus of _Acasta sulcata_. _i_, upper articulation of the lower } _These two letters segment of pedicel. } apply to all the _k_, upper articulation of the upper } figures 1 to 6._ segment of pedicel. } _l_, curved teeth on the pedicel. _m_, " " on the segments of the anterior ramus. 3, Third cirrus of _Chthamalus antennatus_. 4, Second cirrus of _Balanus perforatus_, viewed exteriorly and laterally. 5, Third cirrus of _Xenobalanus globicipitis_. 6, Sixth " " " 7, Spermatozoa (copied from Mr. C. Spence Bate, in 'Annals and Mag. of Natural History' (S. 2), vol. viii, Pl. VIII). _a_, of _Verruca Strömia_, in an early condition. _b_, of _Balanus balanoides_, more mature. _c_, of _Balanus perforatus_, apparently mature. 8, Larva of _Scalpellum vulgare_, immediately after coming out of the egg, seen on the ventral surface (letters of reference given below). 9, Larva of _Balanus balanoides_, immediately after coming out of the egg, seen on the ventral surface, copied from Mr. C. Spence Bate's drawing in 'Annals and Magazine of Natural History' (S. 2), vol. viii, Plate VI, fig. 1 (letters of reference given below). 10, Larva of _Chthamalus stellatus_, after the first moult, but during the first stage, seen on the ventral surface, copied; with some alterations, from Mr. C. Spence Bate's drawing in 'Annals and Magazine of Natural History' (2 Ser.), vol. viii, Plate VIII, fig. 13.

(_The following letters apply to above figs. 8, 9, 10._) _a_, eye. _b_, first pair of antennæ, not observed in fig. 9. _b′_, the same antennæ, as yet encased (in fig. 8) within small horns. _c_, horns, including the second pair of antennæ. _d_, mouth, probosciformed: in fig. 8, the specimen having been acted on by potash, the œsophagus can be seen within, with the orifice beneath the swelling, which latter perhaps answers to the labrum. _e_, first, uniramous natatory leg (homologically the second thoracic limb). _f_ _g_, second and third, biramous natatory legs (homologically the third and fourth thoracic limbs.) _h_, posterior point of carapace. _i_, forked terminal projection of the body or abdomen. _l_, second forked projection. _m_, two sharp points, apparently representing a third forked projection. _n_, a rounded swelling, apparently lying between the carapace and the supposed abdomen, and believed to form the anus.

PLATE 30.

LARVÆ OF LEPAS: SECOND AND LAST STAGES OF DEVELOPMENT.

Fig. 1, Larva of Lepas in the second stage of development; _a_, supposed antennæ (second pair); _m_, mouth; _c_, three pairs of legs. (Copied from Burmeister's 'Naturgeschichte der Rankenfüsser,' Tab. 1, fig. 3.) 2, _Lepas australis_: pupa or larva (2 _a_, of natural size) in the last stage of development, with the young cirripede in its natural position, obscurely seen within,--the specimen having been treated with caustic potash, _and so rendered transparent_,--viewed laterally and greatly enlarged. Scarcely more than the outline of the shell or carapace is represented. The darkly shaded part to the left represents the extent of the sack of the pupa, or the cavity occupied by the thorax, with its limbs. _a_, both antennæ, adhering by their discs to a piece of wood. _b_, dorsal surface of the shell or carapace; and immediately underneath this letter is the point of reflection of the membrane investing the thorax, so as to line the sack of the pupa. _b′_, is the posterior end of the animal, and of the orifice on the ventral surface, through which the legs are protruded. _c_, six pairs of natatory legs. _d_, pair of caudal appendages, seated on a minute abdomen. _m_, mouth, from which the œsophagus can be seen running into the stomach, the latter having two dark cæca; the stomach sweeps round in the pupa to the abdomen, near _b′_; but in the young included cirripede, only as far as the letter (_b_), where the bases of the posterior pair of cirri and the anus lie. _n_, apodemes, supporting the eyes, produced deeply inwards from the eye-bearing segment (N, in fig. 4) of the antennæ. _s_, bottom of sack of the young cirripede immediately after its metamorphosis; it extends as far as _s′_. (See _s_, in fig. 3.) _t_, gut-formed cement-gland (or incipient ovaria), seen on the near side of the animal, whence a cement-duct, _t′_, runs into the near antenna. _u_, internal and anterior part of the pupa, filled with pulpy, oily matter, together with the incipient muscles of the peduncle; when stretched out it forms the peduncle of the young cirripede. See _u′_, in fig. 3. _x_, bases of the pedicels of the cirri of the young included cirripede. 2 _a_, Pupa of _Lepas australis_ of natural average size, within a half-inch wide. 3, Young cirripede (on a smaller scale than Fig. 2), immediately after the exuviation of the bivalve-like pupal carapace, the basal segments of the antennæ, the eye-apodemes and eyes. The young cirripede has just assumed its proper position at nearly right angles to what it held whilst packed within the pupa,--this change of position having been effected by the opening out or stretching of the deep fold of membrane (see _n_, in fig. 2) formed over the eye-apodemes and eyes, previous to the act of exuviation. _a_, the three terminal segments of the antennæ of the pupa, still remaining cemented, in the same position as before, to the same piece of wood: the basal, or eye-bearing segment (N, in fig. 4), has been moulted with the pupal carapace. _c_, _d_, legs and caudal appendages of the pupa, not as yet moulted, but quite functionless; the external membrane of the thorax, and that lining the sack of the pupa, are, likewise, as yet retained, but soon will be cast off. _s_, bottom of the sack of the young cirripede, which can now be easily distinguished. _u′_, the peduncle. _x_, _y_, _z_, primordial valves, composed of chitine: _x_, being the scutum; _y_, the tergum; _z_, the carina. 3 _a_, small portion of one of the primordial, non-calcified valves, much magnified. 4, ventral surface of pupa; on the same scale, and in the same semi-transparent condition as in fig. 2. _a_, antennæ. _b_, limit of sack on the sides in the ventral or lower half of the pupa. _b′_, posterior end of the carapace. _c_, _d_, bristles of the natatory legs and of the caudal appendages, protruded through the orifice of the carapace. _e_, orifice of the acoustic sacks. _m_, mouth, with the œsophagus attached to it, obscurely seen through the carapace; the stomach having been removed. _n_, apodemes supporting the eyes. N, the eye-bearing or basal segments of the antennæ. _o_, the second or main segment of the antennæ. _p_, the third or disc segment of the antennæ. _v_, the fourth or terminal segment of the antennæ. W, ventral surface, bordered by the edges of the carapace; the letter stands near the extremity of the œsophagus. 5, First pair of natatory legs: _f_, lower segment of pedicel; _g_, upper segment of pedicel; _h_, lower segment of ramus; _i_, upper segment of ramus; _k_, outer ramus; _l_, inner ramus of same leg; _r_, sternal surface between the first and second pairs of legs, with singular thickened ridges and folds. 6, Abdomen with two caudal appendages: ^1, first abdominal segment, attached to the posterior thoracic segment; ^2, second abdominal segment; ^3, third or last abdominal segment; _h_, lower segment; _i_, upper segment of caudal appendage. 7, Transverse section of the pupa, close to the eye-apodemes; these being made to stand more upright than in fig. 2. The internal organs of the animal have all been removed. _a a a′_, section of carapace; from _a_ to _a′_, on the lower side, forms the ventral surface, with three longitudinal furrows, here in some degree opened out. _c_, crest of thick membrane on each side, forming the sides of the lateral furrows. N, the posterior margin of the eye-bearing segment (see fig. 4) of the antennæ; the edges of which are hardened and thickened, and are produced inwards, forming _n_, the apodemes, to which are attached the (_n′_) great compound eyes. 8, Terminal portion of an antenna, greatly magnified, seen from above. _o_, part of the second or main segment; an oblique line shows a line of separation of the upper thinner and lower thicker membrane; _o′_, single spine borne at this segment. _p_, disc-segment, bearing seven spines; _p′_, an irregular border of the cement-tissue, believed to have debouched through the spoke-like minute tubes seen on the disc. _v_, terminal segment, projecting almost rectangularly outwards; _v′_, most delicate tube or ribbon, believed to consist of cement-tissue.

ERRATA.

Page

104, thirteen lines from bottom, _for_ "_Balanus elongatus_," _read_ "_Balanus galeatus_."

105, six lines from bottom, _for_ "_Balanus elongatus_," _read_ "_Balanus galeatus_."

174, Since the table on the distribution of the fossil species was drawn up, I have examined some more specimens, sent me by Mr. Wood, which show that _Balanus concavus_ and _Hameri_ are found in the Red Crag; and that _Verruca Strömia_ is found in the Coralline Crag; this will make the total in the Coralline Crag ten, and in the Red Crag eight. I should, however, add, that the identification of _Verruca Strömia_ in the two Crags is a little doubtful, as the specimen was without the opercular valves.

235, to _Fossil_ localities of _Bal. concavus_, add Red Crag (Sutton) Mus. S. Wood.

255, six lines from the top, _Bal. crenatus_, I have now seen a single Red Crag specimen .5 of inch in basal diameter.

278, to _Fossil_ localities of _Bal. Hameri_, add Red Crag (Sutton) Mus. S. Wood.

293, nineteen lines from the top, _for_ "Cotantin," _read_ "Cotentin."

300, ten lines from bottom, _for_ "parieted" _read_ "parietal."

INDEX.

N.B. The names in _italics_ are synonyms or doubtful species.

Abdomen of the Balanidæ, 65. of larvæ in first stage, 108. in pupa of Alcippe, 548.

Abdominalia, order of, 21, 563.

Acasta, sub-genus, 302. cyathus, 312. fenestrata, 316. glans, 314. lævigata, 315. _Montagui_, 308, 492. purpurata, 318. _spinulosa_, 321. spongites, 308. sporillus, 319. sulcata, 310. _tubulosa_, 320. undulata, 313.

Acorn shell, 33.

Adductor scutorum, 53.

_Adna_, genus, 354. _Anglica_, 360.

Affinities of the Balanidæ, 152.

Alæ, structure of, 37, 47.

Alcippe, genus, 529. lampas (female), 530. lampas (male), 555. sexes of, 23.

Anelasma, false, resemblance to Xenobalanus, 445. compared with Alcippe, 528.

Antennæ of larva in first stage, 105. of pupa, 114. of Alcippe, 549. of Cryptophialus, 581. of Proteolepas, 601.

Anus, 87. none in Proteolepas, 596. none in the male Alcippe and Cryptophialus, 546, 562, 585.

Apoda, order of, 22, 587.

Apodemes for the attachment of eyes of pupa, 120, 126.

Apparatus, cementing, 133.

Appendages, caudal, 65, 85, 479, 481, 491. in Verruca, 510. in Alcippe, 543. filamentary, to sack, 64. to limbs, 64, 83.

_Asemus_, genus, 321. _porosus_, 329.

_Astrolepas_, genus, 382. _lævis_, 396. _rotundarius_, 392.

Attachment of Chelonobia to turtles, 390. of Coronula to whale's skin, 411. of Tubicinella, 436.

Baer, Von, on morphological differentiation, 19.

Balanidæ, family of, 33. highest Cirripedes, 20.

Balaninæ, sub-family of, 175. characters of, 152.