« PreviousContinue »
ANIMATED NATURE AS DEVELOPED IN BARBADOS.
As far as the limits of this work permitted, I have already mentioned infusory animalcules in giving a description of the fossil Polycystina. I shall now allude briefly to the succeeding class in the ascending scale, namely, Zoophytes, which obtained their name from an opinion that they were intermediate between animals and vegetables. We meet forms among these remarkable submarine bodies which would cause us to doubt at first sight whether we see the petrified branch of a tree before us, or the production of minute animals. If our eye could penetrate to the submarine regions, we should there observe structures similar to our meadows, groves and forests in colour and appearance; we should observe forms which cover the bottom of the sea with a luxuriance, which persons unacquainted with the fact, fancy belongs only to regions warmed by the congenial rays of the sun; indeed, to use the words of the poet,
"There with a slight and easy
The fan-coral sweeps through the clear deep sea,
Are bending like corn on the upland sea.”
Instead of leaves and flowers, the coralline groves are clothed with buds or gems. The surface of the branches are enlivened by small animals, provided with several long feelers, now expanding their bodies, then suddenly closing or withdrawing into their cells.
In their outward appearance we might compare the ramiferous species to a tree with its numerous branches and interlacing twigs, all arising from a common stem. In the tree, these branches and leaves serve for the nourishment of the individual tree, in the coral it is an assemblage or aggregation of individuals, which Professor Forbes has very happily compared to the commonwealth of bees in their hive, or of termites in their hill. In the coral, each individual is characterized by having a single mouth, provided with tentacula eager to satisfy its appetite, and yet the whole coral-tree is animated by a common principle of life and growth. If one of the branches of the stony corals is broken off, the rugged and irregular surface will be found covered with a mucous fluid studded with little jelly-like drops. These are the polypi, in that state an unshapen mass; but let them be observed in their element, and when un
disturbed, then the stony coral will be seen covered with infinite numbers of animalcules, each issuing from its cell, enjoying the power of voluntary motion, and spreading abroad its feelers in order to seize its prey, while the hinder part still remains attached to its stony house; but on the least approach of danger they suddenly close and withdraw in their habitation. It is obvious then that they possess their movements, their appetites and their instincts. The body of the individual, which is called a polypus from the supposed resemblance of the tentacula or feelers around the central mouth to those of an Octopus (a kind of cuttlefish), is cylindrical or conical. Sometimes the body possesses no other viscus but its cavity; at others a stomach and several organs are clearly visible; and in some instances the viscera of each polypus is enclosed in a double tunic.
There is an analogy in the propagation of Zoophytes with some so-called viviparous and bulbous plants of Endogens; little bulbous gems or buds are formed on the branches or between the leaves of a few monocotyledons, which fall off and become individual plants. In the Zoophyte (e. g. Sertularia), variously formed bodies containing ova spring up from the branches at certain periods, which have been called ovigerous vesicles. The ova that are found in these vesicles separate and become conical, and form ultimately a cell which assumes a calcareous consistency, and out of the summit of which the new polypus issues.
The Madrepora and Astrææ are the genera which are principally occupied in erecting coral reefs. They are generally found in a zone extending twenty-eight degrees north and south of the equator. Their northern extremity is Bermuda (in 32° 19′ latitude), where most likely the Gulf-stream keeps the surrounding sea at a temperature of 66° or 68° Fahr. I have already stated Mr. Darwin's opinion that reef-building corals do not flourish at a greater depth than between twenty and thirty fathoms; and Mr. Dana considers that a depth of twenty or perhaps sixteen fathoms will include very nearly all the species of the Madrepore and Astræa tribes. Temperature has little or no influence in occasioning these limits, as 68° Fahr. will not be found under the equator short of a depth of a hundred fathoms. Light and pressure are most likely the principal causes in the limitation of the depth where they can exist. The geographical distribution of the genera is very curious; according to Mr. Dana, the species of corals in the West Indies are in many respects peculiar, and not one can with certainty be identified with any of the East Indies. Meandrina labyrinthica and Astræa galaxea seem the only two which are to be met with in both hemispheres.
The West Indies possess of the tribe Astræacea (Dana) thirty-five genera, of Caryophyllacea ten, and of Madreporacea fifteen. Manicina, Caryophyllia and Oculina are more numerous in the West Indies than elsewhere; and the Ctenophyllie have been found only in that locality. The genus Porites contains several West India species. The beautiful
Seafans and Seafeathers deserve to be especially mentioned, the axis of The species found in the seas near Barbados are
which is corneous. chiefly
Gorgonia pinnata, Lam.1
B. Cortice purpurascente. The purple Seafan.
The Seafeathers are different species of the genera Veretillum, Plumularia and Pennatula; and the Searods are species of Sertularia and Placomus.
The Actinoidea form an order of zoophytes in Mr. Dana's classification2. Cuvier enumerated the genera among his class Acalepha, forming a section of the fourth great division of the animal kingdom, called Radiata.
Lamarck places Actinia under the Fistulide, which form the third section of his Radiata. They possess a cylindrical, fleshy and simple body, very contractile, and attached by its base to some other substance, having however the power of removing itself; the mouth is terminal, margined, with one or several rows of radiated tentacula, which the animal is able to withdraw within the orifice, resembling a flower in blossom when dilated, and when contracted they possess the form of a globular or oval bulb. The extremity of their body is terminated by a flat disc, in the middle of which is the mouth, around which the tentacula are placed. These rays or feelers are said to possess on their extremity a pore with which they are able to seize their prey as if by suction; and it is likewise asserted that they are able to draw in and eject water through these pores. They fix themselves on rocks, shells, or sand, by means of the flattened part of their body, and so nearly even with the water that they are frequently exposed during a rough sea, but as they have the power to remove themselves they can easily avoid the contact with the air, and may select a deeper place.
If an Actinia be cut in several pieces it is asserted that every piece continues to live separately and to develope itself into a new Actinia3. During sunny weather they extend their body and spread out their rays resembling the petals of the marigold, and their fine attenuated ends are in constant play; but upon the slightest approach of danger or a ripple of the water they are withdrawn, the whole body contracts suddenly, and the extremity folds itself inwardly as if it were in a sheath. This movement, which is likewise observed in Holothuria, takes place
1 Other species of the genus Gorgonia which are found in the West Indian archipelago are Gorgonia flavida, hammomella, Richardii, lima, clavaria, mammosa, muricata, &c.
2 James D. Dana on the Geographical Distribution and Classification of Zoophytes. 3 Lamarck doubts this in some respect, but I have heard it asserted as a well-known fact by the fishermen in the Virgin Islands.
frequently, and with much rapidity. They live upon small shrimps, minute crabs, and medusa, which they seize with their feelers, and keep them in their stomachs for ten or twelve hours, after which the indigestible parts are ejected. They frequently seize medusa much larger than themselves. The fishermen, who are well acquainted with their manner, are able to predict, from the state in which their rays are unfolded entirely or partly, whether fair or bad weather, and a smooth or a rough sea is to be expected: indeed they serve these people as a barometer. The following species of Actinia, or Animal flowers, have been observed around Barbados :—Actinia annulata, Lesueur (its length is from 2 to 3 inches, and its breadth from 2 to 3 lines), and Actinecta olivacea, Lesueur.
In the genus Zoanthus several bodies adhere to a tubular root common to all. The animal is about two inches long, and is permanently fixed, e.g. Zoanthus socialis, Lesueur, Zoanthus Solanderi, &c. Mammillifera auricula and M. nymphæa, Lesueur, are likewise found among the coral reefs on the windward shore.
Closely allied to Actinia are the Holothuria, known under the name of Marrow Puddings or Sea-suckers. Sipunculus is called by the fishermen of Barbados Sea-cow'. They belong to the class Echinodermata, tribe Fistulida, and are covered with a thick coriaceous skin, which, by means of longitudinal and circular bands of muscular fibres, the animal can shorten or lengthen. The Holothuria are of a cylindrical form, tapering towards the end, dark brown, and have received their common name from their resemblance to a black pudding. The Sipunculus edulis, which is considered a great delicacy in Java and China, is of a flesh colour.
The Medusa are those remarkable bodies which we see floating about on the surface of the sea, and which are better known under the name of Sea-nettles or Blubber; the Velella mutica, or Sally-man, and V. tropica, with bluish membrane, belong to this section. Different species of Medusa are highly phosphorescent, and the luminous appearance of seawater is ascribed to immense numbers of microscopic species floating on the surface of the sea, chiefly in warmer climes. The pretty Portuguese Men-of-war belong likewise to this order; the one margined red is Physalia pelagica, and the other margined blue, P. tuberculosa. The French call them Gallère or Frégate.
The Sea Stars or Star-fish (Stellerida) consist of bodies divided into angles or arms, furnished with numerous retractile tentacula. They have their mouth in the centre, and placed downwards. The Asteria tessellata and Asteria rubens, the latter with five lobes or rays, inhabit almost all seas. The Sea-spider or Sea-scorpion of Hughes is Ophiura echinata, Lam., and the Caput Medusa, Euryale caput Medusa.
The Sea-eggs or Sea-urchins (Echinus) are covered by a hard and cori
1 I need scarcely observe that the true sea-cow is a cetaceous animal, and belongs to the genus Manatus (M. americanus).
aceous skin. The shell is spherical, and consists of polygonal plates, fitting closely to each other, and is covered with many spines or prickles, by means of which they are able to move from place to place. The mouth is seated in the under surface. They are used as an article of food by all classes in Barbados, and are considered in season when they are with ovula or spawn. The eggs are of a red appearance, and granular; and according to the fishermen, who ascribe great powers to the influence of the moon, they are better tasted in the full than in the wane of that luminary.
The great black shooting Sea-egg is Echinus esculentus. Hughes relates that this species is able to dart its large prickles with such violence that he has known the animal to strike or dart them through the thick fleshy part of the toe-nail of a fisherman: this assertion wants to be confirmed before we can adopt it. They frequent mostly the bottom of fine sandy bays, where they are found in seven to eight feet of water. The E. esculentus is very abundant on the north-eastern coast of the island, near Conset's Bay. The other species of sea-eggs about Barbados are Echinus variegatus, Lam., E. ventricosus, E. Maugei, &c. The closely allied Spatangus Atropos, Lam., is the " tête de mort," or death's head.
The shells of Echinanthus are of an irregular figure, somewhat flat, and resemble a buckler. The concave surface is divided by punctures into the appearance of five narrow rosaceous leaves, which terminate at the mouth in the centre. The whole of the surface is marked with small depressions of a circular form, with central tubercles, and covered with very small spines. The species are known in Barbados by the name of the Platefish or flat Sea-eggs.
There is a rule which we see pervading the wonderful works of creation-that the nobler the animal, the more slow is its production. It appears as if nature acted with a kind of dignified economy in the development of the higher ranks of animal life, while she is lavish in the production of the lower forms. This observation refers likewise to insects; their number in some instances almost surpasses belief. The female of the white ant is said to lay no fewer than forty or fifty millions of eggs in a year, and Aleyrodes proletella, a small hemipteron, two hundred thousand. Their amazing number is also an argument of their imperfection, and they present in their formation no internal skeleton, a body covered by a coriaceous or membranous integument, and divided into three distinct sections, namely the head provided with two antennæ, the thorax with six articulated legs, and the abdomen. Their nervous system is composed of ganglions; they possess an imperfect circulating system, respiration by means of tracheæ communicating with the air by stigmata, and are oviparous. They pass through several transformations and changes, called their metamorphoses. Some authors have called them Annulata,