Read Ebook: A Monograph on the Sub-class Cirripedia (Volume 1 of 2) The Lepadidae; Or Pedunculated Cirripedes by Darwin Charles

Font size: 10 px 15 px 20 px 25 px 30 px 35 px

Background color: BlackWhiteGrayLight GrayDark GrayDim Gray

Text color: BlackWhiteGrayLight GrayDark GrayDim Gray

Apply/Save settings

Ebook has 622 lines and 140161 words, and 13 pages

THE

RAY SOCIETY.

LONDON.

A MONOGRAPH

ON THE SUB-CLASS

CIRRIPEDIA,

WITH

FIGURES OF ALL THE SPECIES.

CHARLES DARWIN, F.R.S., F.G.S.

THE LEPADIDAE;

OR,

PEDUNCULATED CIRRIPEDES.

LONDON:

PRINTED FOR THE RAY SOCIETY.

C. AND J. ADLARD, PRINTERS, BARTHOLOMEW

PREFACE

My duty, in acknowledging the great obligations under which I lie to many naturalists, affords me most sincere pleasure. I had originally intended to have described only a single abnormal Cirripede, from the shores of South America, and was led, for the sake of comparison, to examine the internal parts of as many genera as I could procure. Under these circumstances, Mr. J. E. Gray, in the most disinterested manner, suggested to me making a Monograph on the entire class, although he himself had already collected materials for this same object. Furthermore, Mr. Gray most kindly gave me his strong support, when I applied to the Trustees of the British Museum for the use of the public collection; and I here most respectfully beg to offer my grateful acknowledgments to the Trustees, for their most liberal and unfettered permission of examining, and when necessary, disarticulating the specimens in the magnificent collection of Cirripedes, commenced by Dr. Leach, and steadily added to, during many years, by Mr. Gray. Considering the difficulty in determining the species in this class, had it not been for this most liberal permission by the Trustees, the public collection would have been of no use to me, or to any other naturalist, in systematically classifying the Cirripedes.

Previously to Mr. Gray suggesting to me the present Monograph, Mr. Stutchbury, of Bristol, had offered to intrust to me his truly beautiful collection, the fruit of many years' labour. At that time I refused this most generous offer, intending to confine myself to anatomical observations; but I have since accepted it, and still have the entire splendid collection for my free use. Mr. Stutchbury, with unwearied kindness, further supplied me with fresh specimens for dissection, and with much valuable information. At about the same period, Mr. Cuming strongly urged me to take up the subject, and his advice had more weight with me than that of almost any other person. He placed his whole magnificent collection at my disposal, and urged me to treat it as if it were my own: whenever I told him that I thought it necessary, he permitted me to open unique specimens of great value, and dissect the included animal. I shall always feel deeply honoured by the confidence reposed in me by Mr. Cuming and Mr. Stutchbury.

Had it not been for the Ray Society, I know not how the present volume could have been published; and therefore I beg to return my most sincere thanks to the Council of this distinguished Institution. To Mr. G. B. Sowerby, Junr., I am under obligations for the great care he has taken in making preparatory drawings, and in subsequently engraving them. I believe naturalists will find that the ten plates here given are faithful delineations of nature.

I have given the specific or diagnostic characters, deduced from the external parts alone, in both Latin and English. As I found, during the progress of this work, that a similarly abbreviated character of the softer internal parts, was very useful in discriminating the species, I have inserted it after the ordinary specific character.

In those cases in which a genus includes only a single species, I have followed the practice of some botanists, and given only the generic character, believing it to be impossible, before a second species is discovered, to know which characters will prove of specific, in contradistinction to generic, value.

In the Rules published by the British Association, the 12th edition, is specified, but I am informed by Mr. Strickland that this is an error, and that the binomial method was followed in the 10th edition.

The Lepadidae, or pedunculated Cirripedes, have been neglected under a systematic point of view, to a degree which I cannot quite understand: no doubt they are subject to considerable variation, and as long as the internal surfaces of the valves and all the organs of the animal's body, are passed over as unimportant, there will occasionally be some difficulty in the identification of the several forms, and still more in settling the limits of the variability of the species. But I suspect the pedunculated Cirripedes have, in fact, been neglected owing to their close affinity, and the consequent necessity of their being included in the same Work with the Sessile Cirripedes; for these latter will ever present, I am fully convinced, insuperable difficulties in their identification by external characters alone.

I will here only further remark, that in the Introduction I have given my reasons for assigning distinct names to the several Valves, and to some parts of the included animal's body; and that in the Introductory Remarks, under the general description of the Lepadidae, I have given an abstract of my Anatomical Observations.

CORRIGENDA AND ADDENDA.

Page

MONOGRAPH

THE CIRRIPEDIA.

INTRODUCTION.

I should have been enabled to have made this Volume more complete, had I deferred its publication until I had finished my examination of all the other known Cirripedes; but my work would thus have been rendered inconveniently large. Until this examination is completed, it will be more prudent not to discuss, in detail, the position of the Lepadidae amongst the Cirripedia, or of these latter in the great class of Crustacea, to which they now, by almost universal consent, have been assigned. I may, however, remark that I believe the Cirripedia do not approach, by a single character, any animal beyond the confines of the Crustacea: where such an approach has been imagined, it has been founded on erroneous observations; for instance, the closed tube within the stomach, described by M. Martin St. Ange , as indicating an affinity to the Annelides, is, I am convinced, nothing but a strong epithelial lining, which I have often seen ejected with the excrement. Again, a most distinguished author has stated that the Cirripedia differ from the Crustacea:--1st. In having "a calcareous shell and true mantle;" but there is no essential difference, as shown by Burmeister, in the shells in these two classes; and Cirripedes certainly have no more claim to a mantle than have the bivalve entomostraca. 2d. "In the sexes joined in one individual;" but this, as we shall see, is not constant, nor of very much weight, even if constant. 3d. "In the body not being ringed;" but if the outer integument of the thorax of any Cirripede be well cleaned, it will be seen, , to be most distinctly articulated. 4th. "In having salivary glands;" but these glands are, in truth, the ovaria. 5th. "In the liver being formed on the molluscous type;" I do not think this is the case, but I do not quite understand the point in question. 6th. "In not having a head or organs of sense;" this is singularly erroneous: Professor Leidy has shown the existence of eyes in the mature Cirripede; the antennae, though preserved, certainly become functionless soon after the last metamorphosis; but there exist other organs of sense, which I believe serve for smelling and hearing: and lastly, so far from there being no head, the whole of the Cirripede externally visible, consists exclusively of the three anterior segments of the head.

NOMENCLATURE OF THE VALVES.

I have unwillingly found it indispensable to give names to several valves, and to some few of the softer parts of Cirripedes. The accompanying figure of an imaginary Scalpellum includes every valve; the two most important valves of Lepas are also given, in which the direction of the lines of growth and general shape differ from those of Scalpellum as much as they do in any genus. The names which I have imposed will, I hope, be thus acquired without much difficulty.

In the Carina of Fossil Species of Scalpellum, I have found it necessary to distinguish different parts, viz., A, the tectum, of which half is seen; B, the parietes; and C, the intra-parietes.

As each valve often requires a distinct description, I have found it indispensable to give names to each margin. These have mostly been taken from the name of the adjoining valve, In Lepas, Pollicipes, &c., the margin of the scutum adjoining the tergum and upper latus, is not divided into two distinct lines, as it is in Scalpellum, and is therefore called the Tergo-lateral margin. In Scalpellum these two margins are separately named Tergal and Lateral. The angle formed by the meeting of the basal and lateral or tergo-lateral margins, I call the Baso-lateral angle; that formed by the basal and occludent margins, I call, from its closeness to the Rostrum, the Rostral angle. In Pollicipes the carinal margin of the tergum can be divided into an upper and lower carinal margin; of this there is only a trace in Scalpellum.

I have followed the example of Botanists, and added the interjection to synonyms, when I have seen an authentic specimen bearing the name in question.

Every locality, under each species, is given from specimens ticketed in a manner and under circumstances appearing to me worthy of full confidence,--the specific determination being in each case made by myself.

CLASS--CRUSTACEA. SUB-CLASS--CIRRIPEDIA.

FAMILY--LEPADIDAE.

Cirripedia having a peduncle, flexible, and provided with muscles. Scuta furnished only with an adductor muscle: other valves, when present, not united into an immovable ring.

Metamorphoses; larva, first stage, pp. 9-12; larva, second stage, p. 13; larva, last stage, p. 14; its carapace, ib.; acoustic organs, p. 15; antennae, ib.; eyes, p. 16; mouth, p. 17; thorax and limbs, p. 18; abdomen, p. 19; viscera, ib.; immature cirripede, p. 20; homologies of parts, p. 25.

Description of mature Lepadidae, p. 28; capitulum, ib.; peduncle, p. 31; attachment, p. 33; filamentary appendages, p. 38; shape of body, and muscular system, p. 39; mouth, ib.; cirri, p. 42; caudal appendages, p. 43; alimentary canal, 44; circulatory system, p. 46; nervous system, ib.; eyes, p. 49; olfactory organs, p. 52; acoustic organs, p. 53; male sexual organs, p. 55; female organs, p. 56; ovigerous lamellae, p. 58; ovigerous fraena, ib.; exuviation, p. 61; rate of growth, ib.; size, ib.; affinities of family, p. 64; range and habitats, p. 65; geological history, p. 66.

The meaning of this and all other terms is given in the Introduction, at pp. 3-7.

Philosophical Transactions, 1835, p. 355, Pl. vi.

Beitr?ge zur Naturgeschichte der Rankenf?sser, 1834. Mr. J. E. Gray, however, briefly described, in 1833, the larva in the first stage of Balanus; in this notice the anterior end of the larva is described as the posterior.

Edinburgh New Philosophical Journal, July 1843, Pls. iii and iv.

This will appear in the October number of the 'Annals of Natural History.'

There are three pairs of limbs, seated close together in a longitudinal line, but some way apart in a transverse direction: the first pair always consists of a single spinose ramus, it is not articulated in Scalpellum, but is multi-articulate in some genera; it is directed forwards. The other two pair have each two rami, supported on a common haunch or pedicel: in both pair, the longer ramus is multi-articulate, and the shorter ramus is without articulations, or with only traces of them: the longer spines borne on these limbs are finely plumose. The abdomen terminates, a little beyond the posterior end of the carapace, in a slightly upturned horny point; a short distance anteriorly to this point, a strong, spinose, forked projection depends from the abdominal surface.

The first pair of legs answers, as I believe from reasons hereafter to be assigned, to the outer pair of maxillipods in the higher crustacea; and the other four legs to the first two pair of thoracic limbs in these same crustacea; this being the case, the highly remarkable position of the mouth in the larva, either between the bases of the two posterior pair of legs, or at least posteriorly to the first pair, together with the probable functions of the spiny points springing from the basal segments of the two hinder pair of true thoracic limbs, forcibly bring to mind the anomalous structure of the mouth being situated in the middle of the under side of the thorax, in Limulus,--that most ancient of crustaceans, and therefore one likely to exhibit a structure now embryonic in other orders. I will only further remark, that I suspect that the truncation of the anterior end of the carapace, has been effected by the segments having been driven inwards, and consequently, that the larger antennae within the lateral horns, though standing more in front than the little approximate pair, are normally the posterior of the two pair. According to Milne Edwards, the posterior pair are normally seated outside the anterior pair, and this is the case with those within the lateral horns.

Beitr?ge zur Naturgeschichte der Rankenf?sser, s. 16, Tab. i, figs. 3, 4.

Share on: WhatsApp @Hash Facebook Tweet