Ctenophora

“ Tentacles.—In all the Ctenophora, except the Beroidae and the adult stages of Lobata and Cestoidea, there is a single pair of tentacles. They are attached to the base of a blind funnel-shaped pit which opens to the exterior near the equator of the animal's body. The pits are on opposite sides of the body, and the plane which passes through them both vertically divides the body into approximately equal parts. ”

“ There can be but little question of the propriety of including Ctenophora among the Coelentera. The undivided coelenteron (gastro-vascular system) which constitutes the sole cavity of the body, the largely radial symmetry, the presence of endodermal generative organs on the coelenteric canals, the subepithelial nerve-plexus, the mesogloea-like matrix of the body—all these features indicate affinity to other Coelentera, but, as has been stated in the article under that title, the relation is by no means close. ”

“ At Valencia it is common in August and September, and sometimes reaches the great size of 90 mm. in length by 50 mm. in breadth. It is usually of a pale pink colour.
Appendix to Ctenophora
Hydroctena salenskii has recently been discovered by Dawydoff [435] floating with the Plankton off the island Saparua in the Malay Archipelago. It is claimed to be a connecting link between the Ctenophora and the Medusae of the Hydrozoa.
In external features it is like one of the Narcomedusae, having a transparent jelly-like bell with a wide bell-mouth guarded by a velum (Fig. 184, V) . ”

“ Sexual Organs.—Most of the Ctenophora are undoubtedly hermaphrodite, but Willey was unable to find ova in some of his specimens of Ctenoplana that were producing spermatozoa. In the Cydippidea the ova are produced on one side of the longitudinal canal and the spermatozoa on the other. Each longitudinal canal therefore performs the functions of a hermaphrodite gland. When the sexual cells are ripe they escape into the infundibulum and are discharged by the mouth. In Ctenoplana there are definite and direct male genital ducts. ”

“ Although the fresh-water Hydra may be regarded as typical of this group of animals, marine fauna furnish a far more extensive group in the corals, jelly-fish, and sea-anemones.
A smaller group, the Ctenophora, although members of this sub-kingdom, have not yet found their true position; nevertheless they are interesting glassy, transparent creatures, either shaped like apples, melons, or Phrygian caps, or else forming bands of some considerable length; all are wonderfully transparent, with the single exception of the Beroë. ”

“ Indeed, the beginnings of such a system can be seen in the Ctenophora, in which there are small excretory organs opening into the digestive cavity. The corresponding organs in the worms, as in all subsequent types, open directly to the outside. In the Turbellarians these organs, which are termed nephridia, are two in number, and consist of long tubes which branch and ramify throughout the body, the small branches terminating in special excreting cells, and the whole constituting a complete and thorough drainage system. ”

“ This difference is best marked in the Phæoconchia, whose bivalved lattice-shells have as their ground-form the rhomboid pyramid of Ctenophora. In most Phæogromia the monaxon lattice-shell may develop simultaneously by sudden excretion at a particular moment of lorication; this is also the case with the polyaxon lattice-shells of the Phæosphæria. In their future growth the development of basal or radial apophyses is of special importance. In the majority of the Phæodaria these apophyses are tubes of silicate filled with jelly (often provided with an axial siliceous thread) ”

“ It is flattened along the axis which unites sense-organ and mouth, so as to give it a dorsal (aboral) surface, and a ventral (oral) surface on which it frequently creeps. Its costae are very short, and retrusible; its two tentacles are pinnate and are also retrusible. ”

“ It is the Cetonia. The handsome insect has [5] not yet recovered from the chill of morning; it lies slumbering all golden on the lilac-blossoms, unconscious of danger, incapable of flight. It is plentiful. Five or six are quickly caught. I intervene, so that the rest may be left in peace. The booty is placed in a box, with a bed of blossoms. Presently, during the heat of the day, the Cetonia, with a long thread tied to one leg, will fly in circles round the little girl’s head.
Childhood is pitiless because it does not understand, for nothing is more cruel than ignorance. ”

“ In order that it may be consumed with the delicate anatomical discretion imposed by the necessity of having fresh food to the last, the Cetonia-grub must be plunged into a state of absolute immobility: any twitchings on its part—as the experiments which I have undertaken go to prove—would discourage our nibbling larva and impede the work of carving, which has to be effected with so much circumspection. It is not enough for the victim to be unable to move from place to place beneath the soil: in addition to this, the contractible power in its sturdy muscular organism must be suppressed. ”

“ After the gastrula stage, which is found as a developmental stage in all Enterozoa, the embryo of the Hydrozoa proceeds to develop characters which are peculiar to the Coelenterata only. Round the blastopore hollow outgrowths, variable in number, arise by the evagination of the entire body-wall, both ectoderm and endoderm. Each outgrowth contains a prolongation of the archenteric cavity (compare figs. 2 and 3, A) . In this way is formed a ring of tentacles, the most characteristic organs of the Cnidaria. ”

“ The Cetonia-larva is worth attention from another point of view. It is a corpulent grub, an inch long, with a convex back and a flat belly. The dorsal surface is wrinkled with thick folds, on which the sparse hairs stand erect like the bristles of a brush; the ventral surface is smooth, covered with a fine skin, through which the ample wallet of ordure shows as a brown patch. The legs are very well-shaped, but are small, feeble and out of proportion to the rest of the body. ”

“ The archenteron becomes the gastrovascular system or coelenteron. Between the ectoderm and endoderm a gelatinous supporting layer, termed the mesogloea, makes its appearance. The gastrula has now become an actinula, which may be termed the distinctive larva of the Cnidaria, and doubtless represents in a transitory manner the common ancestor of the group. In no case known, however, does the actinula become the adult, sexually mature individual, but always undergoes further modifications, whereby it develops into either a polyp or a medusa. ”

“ She knows that her grub will regale itself on what she herself abhors; and overcoming her repugnance, not even giving it a thought, she takes the plunge. Is she actuated by the memory of her larval days? But what memory of food can she have after a year’s interval, above all after an absolute remoulding of her organism? To draw the Cetonia hither, to make her come from the rose to this putrid heap, there is something better than the memory of the belly; there is a blind, irresistible impulse, which acts in the most logical manner under cover of a seeming insanity. ”

“ Now this bank of corruption, warmed by the slow decomposition which is working in it, is a paradise for the Cetoniæ in their larval state. The fat grub swarms there, finding abundant provender in the shape of fermented vegetable matter and an agreeable warmth, even in the heart of the winter.
Four species live here, thriving admirably, despite the annoyance which my curiosity causes them. The most numerous is the Metallic Cetonia (C. metallica, Fab.) . This is the insect that provides me with the greater part of my data. ”

“ Nothing is easier than to rear this grub. A thin box, which hinders evaporation and keeps the provisions fresh, receives the nursling together with a selection of fermented leaves, gathered from the heap of mould. This is enough: my charge thrives and undergoes its transformation in the following year, provided I take care to renew the victuals from time to time. No entomological rearing gives less trouble than that of the Cetonia-larva, with its robust appetite and its vigorous constitution. ”

“ If I replace the flesh of the insect by that of another animal, the ox, for instance, shall I obtain the same results? Logic says yes; and logic is right. I dilute with a few drops of water a little Liebig's extract, that precious standby of the kitchen. I operate with this fluid on six Cetoniae or rosechafers, four in the grub stage, two in the adult stage. At first, the patients move about as usual. Next day, the two Cetoniae are dead. The larvae resist longer and do not die until the second day. All show the same relaxed muscles, the same blackened flesh, signs of putrefaction. ”

“ Fig. 33. Idyia roseola seen from the broad side, half natural size; a anal opening, b lateral tube, c circular tube, d e f g h rows of locomotive flappers. (Agassiz.)
The lowest genus of Ctenophoræ found on our coast, the Idyia (Fig. 33) , has neither the tentacles of the Pleurobrachia, nor the lobes of the Bolina. It is a simple ovate sphere, the interior of which is almost entirely occupied by an immense digestive cavity. ”

“ In Ctenopteryx they have a superficial resemblance to the fins of fishes, consisting of a thin membrane supported by a series of muscular rods.
Chromatophores.—These are characteristic of the Dibranchiata, apparently absent in Nautilus. They are originally single cells of ectodermic origin which sink below the epidermis and become connected with radiating muscular fibres. The cells are single but multinuclear. Different cells contain pigments of different colours, yellow, brown, red or blue. Each cell in life is in constant tremulous movement ”

“ As for the effect on man, there is little foundation for the fear with which centipedes are regarded. Our native species produce, at most, local symptoms,—sometimes severe local pain and swelling,—but there is no authentic record of fatal results. In the tropics, some of the species attain a large size, Scolopendra gigantea reaching a length of nearly a foot. These forms are justly feared, and there is good evidence that death sometimes, though rarely, results from their bite. ”

“ The Cetonia-larva lives in crumbling galleries which it bores in the depths of the soil. Like the sweep who obtains a purchase with his back, loins and knees to hoist himself up the narrow passage of a chimney, it gathers itself up, applies the tip of its belly to one wall of its gallery and its sturdy back to another; and the combined effort of these two levers results in moving it forward. The legs, which are used very little, indeed hardly at all, waste away and tend to disappear, as does any organ which is left unemployed ”

“ These orders are distinguished not only by their striking external differences, but by their mode of development also. The Ctenophoræ grow from eggs by a direct continuous process of development, without undergoing any striking metamorphosis; the Discophoræ, with some few exceptions, in which they develop like the Ctenophoræ from eggs, begin life as a Hydra-like animal, the subsequent self-division of which gives rise, by a singular process, presently to be described, to a number of distinct Jelly-fishes ”

“ I remember seeing a huge oriental centipede exhibited in a herbalist's window in a large town in Yorkshire, as having been an inmate of the stomach of a human being.
I have heard the same story as that told me in Devon, repeated in Sussex with this variation, that instead of an earthworm tempting the newt from its retreat, a roast leg of mutton was exhibited at the mouth of the patient. A friend of mine was warned by an old woman in Staffordshire not to eat cress from a brook, on the ground that an acquaintance of hers had once thus swallowed toad-spawn which had been hatched within her. ”

“ All the Ctenophoræ are reproduced from eggs, these eggs being so transparent that one may follow with comparative ease the changes undergone by the young while still within the egg envelope. Unfortunately, however, they are so delicate that it is impossible to keep them alive for any length of time, even by supplying them constantly with fresh sea-water, and keeping them continually in motion, both of which are essential conditions to their existence. ”

“ The Cetonia does not display this haste. She was a gross eater in her days of pot-bellied grubhood; she remains a gross eater beneath the splendour of her adult cuirass. She spends her life, so long as the heat is not too overwhelming, in the jam-factory of the orchard: apricots, pears, peaches, figs and plums. Lingering over her meal, she forgets all else and defers her egg-laying to the following year. ”

“ Throughout the day, centipedes hide under rocks, boards, or bark and in cracks, crevices, closets, basements, and other moist, protected locations. At night, they come out of hiding to hunt for prey which usually consists of insects and other small arthropods. 9 Centipedes inject venom through two powerful claws located on the ventral side of the body immediately behind the head. Contrary to popular belief, centipedes cannot inject venom through their numerous legs. The majority of centipedes found in the United States are small and not a threat to man. ”

“ J. Wighton on insect luminosity, seeing that many cases of phosphorescence attributed to worms really come under this head. He says:—
"The Centipede (Scolopendra electrica, L.) is one of the few luminous insects met with in this country. Its specific name electrica seems to be a misnomer; lucifera or phosphorifera would be more applicable. It would take a large number of Centipedes to give a sensible shock, even supposing the creature capable of doing so at all. In other electric animals, as the Torpedo, no flash appears, even when they give a discharge strong enough to stun a horse ”