Zoophyta

“ Fishes alone are well worthy of close observation; and when to these are added odd little reptiles, queer shell-fish, and different classes of the wonderful zoophytes, an aquarium presents a constantly changing picture of the marvels of ocean life.
The zoophytes are the most remarkable of all marine creatures. The name zoophyte comes from two Greek words—zoön, an animal, and phyton, a plant—and therefore has the literal signification of animal-plant.
An important member of the zoophyte family, and one often introduced into aquaria, is the actinia, or sea-anemone, sometimes called sea-rose. ”

“ There is a species of Star-fish, so brittle, that it is quite impossible to touch it without breaking it, or rather it breaks itself, for it seems to have the power of casting off its arms at pleasure. These forms complete the Radiate series of animals, they have nearly all a somewhat regular radiated form, and some of them are very beautiful, such as Sertularia, which grow in communities and form many beautiful branched objects, much resembling sea-weeds and flowers, hence the name Zoophyte, which means animal flowers. ”

“ For who, after all, to take a few broad instances (not to enlarge on the great root-wonder of a number of distinct individuals connected by a common life, and forming a seeming plant invariable in each species) , would have dreamed of the “bizarreries” which these very zoophytes present in their classification?
You go down to any shore after a gale of wind, and pick up a few delicate little sea-ferns. You have two in your hand, which probably look to you, even under a good pocket magnifier, identical or nearly so. ”

“ The Zoophyte belongs to the simplest form of the animal creation. Its body consists merely of a pouch or stomach, with tentacles arranged round the margin, which it can extend at pleasure to supply itself with food. In many species the individuals grow together on a common stem, from which new members are constantly shooting forth like buds from the branches of a tree. ”

“ A species of animals called Zoophytes, by which are meant beings having such an admixture of the characteristics of both plants and animals, as to render it difficult to decide to which division they properly belong. They are animal in substance, possessed indeed of a stomach, but without the other animal characteristics of blood-vessels, bones, or organs of sense; these creatures live chiefly in water, and are mostly incapable of motion: they increase by buds or excrescences from the parent zoophyte, and if cut off will grow again and multiply; each part becoming a perfect animal. ”

“ Of the organisms resulting from the aggregation of such creatures, we see that while some, as the Foraminifera, assume a certain definiteness of form, in their shells at least, others, as the Sponges, are very irregular. The Zoophytes and the Polyzoa are compound organisms, most of which have a mode of growth not more determinate than that of plants. But among the higher animals, we find not only that the mature shape of each species is very definite, but that the individuals of each species differ little in size. A parallel increase of contrast is seen in chemical composition. ”

“ These enormous questions would need an army of workers; and we have not one. The fashion is all for the Mollusc and the Zoophyte. (Zoophytes are plant-like sea-animals, including Star-fishes, Jelly-fishes, Sea-anemones, and Sponges.—Translator's Note.) The depths of the sea are explored with many drag-nets; the soil which we tread is consistently disregarded. While waiting for the fashion to change, I open my harmas laboratory of living entomology; and this laboratory shall not cost the ratepayers one farthing. ”

“ Edward found numerous Zoophytes along the coast, which excited his admiration almost as much as the Star-fish. Of one species, called “dead-men’s [329] paps, sea-fingers, etc.” (Alcyonium digitatum) , he says, “It is frequently brought ashore by the fishermen, attached to shells and stones. It is curious to observe the strange and fantastic forms which these creatures at times assume. They are loathed by the generality of people when found on the sands. ”

“ After a time, however, which frequently extends to some two or three hours, the motion becomes much retarded, and at length after faint struggles, entirely ceases, and the Zoospores then lie as though dead;—not so, nevertheless—they have merely lost the power of locomotion,—the vital principle is still active within them, and they are seen to expand, to become partitioned, and if the species be of an attached kind, each Zoospore will emit from its transparent extremity two or more radicles, whereby it becomes finally and for ever fixed. ”

“ In the vast majority of the polyzoa, marine as well as freshwater, movement is practically confined to the polypide, the external walls of the zoœcium being rigid, the zoœcia being closely linked together and the whole zoarium permanently fixed to some extraneous object. In a few freshwater species belonging to the genera Cristatella, Lophopus, Lophopodella and Pectinatella, the whole zoarium has the power of progression. ”

“ In the life-history of a moss, the plant itself bears only sexual organs: it is the sexual form, and is distinguished as the gametophyte. The zygote (oospore) formed in the sexual act develops into an organism, the sporogonium, which is entirely asexual, producing only spores: it is distinguished as the sporophyte. When these spores germinate, they give rise to moss-plants. Thus the two forms, the sexual and the asexual, regularly alternate with each other—that is, the life-history presents that simple form of polymorphism which is known as alternation of generations. ”

“ In many of them we find instances of that strange process of reproduction by means of zoospores, or moving spores, which so often occurs among their green-spored relations. The zoospores may be well seen in the plants which belong to the genus Ectocarpus, one or two species of which are very common in the summer, spreading in a matted mass over rocks and larger seaweeds, and looking when left by the tide like a layer of withered and rotting leaves. The moving spores are formed in the last cell of each of the fine threads of which the plant is composed. ”

“ The genus is widely distributed and extends from shallow water to depths of 1500 fathoms. Caryophyllia sometimes occurs in clusters which have the appearance of an incipient colony. This may be due to the embryos fixing themselves upon the epitheca of existing individuals and developing there. It is doubtful whether the species ever reproduce asexually either by gemmation or by fission. When the zooid is fully expanded it projects some distance above the corallum and shows a very transparent body-wall with a crown of some fifty tentacles. ”

“ Not a few varieties of the Coral-producing Zoophytes are to be found in actual living reality on our own coasts, where the curious student may examine for himself their habits and general structure. But it is in the warmer regions of the Earth that they are developed in the greatest numbers, and decked in the brightest hues. Those who have seen them through the crystal waters of tropical seas, swarming in countless multitudes on the clear white sand below, speak with enthusiasm of their luxuriant profusion and of their striking beauty. ”

“ The true Zoophytes have all, more or less, the plant-like form, and they readily separate into two great classes, namely, the Anthozoa, or flower-life, and the Polyzoa, or many-life, in which the individuals are associated together in numbers. ”

“ Seeing how very few fossil forms have been described which have any claim to inclusion in this subdivision of the Algae, it is unnecessary to enumerate or define the various families of the Chlorophyceae. It is true that many species have been figured as examples of different genera of green algae, but few of these possess any scientific value. There is, however, one division of the Chlorophyceae, the Siphoneae, which must be treated at some length on account of its importance from a palaeobotanical and geological point of view. ”

“ There are many other genera and species of fresh-water polyzoa besides the Plumatella repens, and they [127] are found attached to sticks, stones, or leaves, generally to the under surface of the latter. They are all objects of great interest and beauty, which, whatever their diversity, conform sufficiently to one type that the student who has observed one, will easily recognise the zoological position of another. They should be viewed by transmitted and by dark-ground illumination, which produces very beautiful effects. ”

“ Biology.—The zoaria of the species of Plumatella are found firmly attached to stones, bricks, logs of wood, sticks, floating seeds, the stems and roots of water-plants, and occasionally to the shells of molluscs such as Vivipara and Unio. Some species shun the light, but all are apparently confined to shallow water. ”

“ Many of the zoophytes spend part of their life in an active free-swimming condition before settling down, becoming attached and thereafter [Pg 93] remaining fixed. In localities near the seashore many animals belonging to this great group can be readily found and observed. The beautiful sea-anemones with their slowly-waving tentacles, the fine many-branched truly plant-like hydroids with their hosts of little buds, and the soft colorless masses of jelly, the jellyfishes, which are cast up on to the beaches by the waves are all animals belonging to the branch Cœlenterata. ”

“ Experimenting upon Alcyonium digitatum, Miss Pratt [369] has found that the zooids seize and swallow various small organisms of a surface-net gathering, and that they will also swallow finely minced fragments of the muscle of fish, but that they reject many kinds of fish ova. In many tropical and some extra-tropical species the superficial canal systems and the inter-mesenterial spaces of the zooids contain a large number of Zooxanthellae, and their presence seems to be associated in some cases with a decided degeneration of the digestive organs. ”

“ All Zoophytes live in water; most of them in the sea, only a very few in fresh water, such as fresh-water sponges (Spongilla) and some primæval polyps (Hydra, Cordylophora) . A specimen of the pretty flower-like forms which are met with in great variety among Zoophytes is given on Plate VII. (Compare its explanation in the Appendix.)
The tribe of animal-plants, or Zoophytes, is divided into two distinct provinces, the Sponges, or Spongiæ, and the Sea-nettles, or Acalephæ (p. 144) . The latter are much richer in forms and more highly organized than the former. ”

“ In coenocytic forms the zoospores would seem to arise simultaneously, probably because many nuclei are already present. The escape of zoospores is effected by the degeneration of the sporangial wall (Chaetophora) , or by a pore (Cladophora) , a slit (Pediastrum) , or a circular fracture (Oedogonium) . Zoospores are of two kinds: (1) Those which come to rest and germinate to form a new plant; these are asexual and are zoospores proper. (2) Those which are unable to germinate of themselves, but fuse with another cell, the product giving rise to a new individual ”

“ Zoophytes are animals every inch of them, however low in the organic scale, and although many of the compound ones imitate the growth of plants and shrubs so exactly in their mode of spreading that it is only by the closest observation we can persuade ourselves they do not belong to the vegetable kingdom. ”

“ They are aquatic and feed on smaller animals and plants or on bits of organic [Pg 143] matter which they capture by means of the currents produced by the vibrating cilia of the "wheel." Small as they are they have a complex body-structure, with well-organized systems of organs. For a long time, however, they were classed by naturalists with the Protozoa on account of their size. They are found all over the world, mostly in fresh water; a few are marine. More than 700 species of them are known. ”

“ That just described is the simplest, consisting merely of a hemispherical ciliated cup, attached to a single thread. It is barely visible to the naked eye. But there is a compound species which I have this year found to be extremely abundant in my aquarium,—whose occupants, both large and small, it excels in singularity and beauty. In structure it is to the simple Vorticella what a many-branched zoophyte is to an Actinia. My attention was first drawn to the presence of this creature by observing some pebbles and fronds of green ulva thickly coated with a fine flocculent down. ”

“ THE MOLLUSCS, ETC. The curious floral forms of the Zoöphytes have, as yet, attracted the greatest degree of attention among the constructors of marine Aquaria; yet other forms of ocean life offer equal, if not superior, opportunities for curious observation, and are equally well calculated to bear the confinement of the tank. Among them all, none more than the Molluscs, especially the shell-bearing division, which merits the careful attention of the student of Nature, as forming some of her most singular manifestations. ”

“ So much for the existence of the Coral Formation. Next comes the question of its origin, with which, of course, we are chiefly concerned. It is now the received belief of all distinguished Naturalists, that these huge and wide-spread masses of limestone rock, against which the breakers of the ocean are ever thundering in vain, are the work of tiny marine animalcules, and chiefly of those seemingly insignificant creatures known by the name of Polyps or Zoophytes. The Zoophyte, they tell us, is a mason who himself produces the stones that he employs in his building. ”