Parapodia

“ Each segment is normally provided on each side with a single or a couple of bundles of chaetae, by means of which locomotion is effected. These, in the free-living forms, are carried at the ends of lateral muscular outgrowths of the body, known as "parapodia," which are practically limbs.
The "head" of the worm generally carries eyes, and frequently more or less elongated tactile organs, the "tentacles" dorsally and "palps" ventrally. ”

“ We do not find in Chaetopoda that parapodia, belonging to primitively post-oral rings or body-segments (called “somites,” as proposed by H. Milne-Edwards) , pass in front of the mouth by adaptational shifting of the oral aperture. (See, however, 8.)
The Arthropoda might be better called the “Gnathopoda,” since their distinctive character is, that one or more pairs of appendages behind the mouth are densely chitinized and turned (fellow to fellow on opposite sides) towards one another so as to act as jaws. This is facilitated by an important general change in the position of the parapodia ”

“ Very usually (but not in the Onychophora = Peripatus) all the parapodia are plated with chitin secreted by the epidermis, and divided into a series of joints—giving the “arthropodous” or hinged character. ”

“ Further, they are developed from the upper surface of the body. Now, in the Annelids the limbs are typically double pairs projected from the sides of the body; the parapodia consist of two branches, notopodium and neuropodium, and the gills when present are modifications of the notopodium. In the Crustaceans this bipartite condition is indicated by the exopodial and endopodial divisions of the limbs. In the adult insect this duplicity has disappeared, unless we recognise in the position of the gill tracheæ the equivalent of the branchiferous notopodium. ”

“ The blood (or "haemal fluid") is driven forwards in the dorsal vessel, and passes backwards in the ventral vessel. Respiration in Nereis is carried on by the whole surface of the body, but naturally with greater activity in the surface of the parapodia, the lobes of which, with their extensive vascular plexus, may be termed "gills"; but it must be borne in mind that these organs have other functions as well.
The coelomic fluid, which fills the general body-cavity, is colourless, and contains amoeboid corpuscles or "leucocytes." ”

“ Posterior lobes of parapodia subcylindrical, a little conically narrowed distad but with apex well rounded, extending ectad or caudoectad; in middle region of body reaching to or a little beyond middle of longer setae, the setae relatively shorter in anterior region. Setae all simple and limbate with the usual double curve, the first curve or angulation obviously less marked than in A. lagunae, which form this species superficially resembles. Number of segments in type, two hundred and seventy-seven. ”

“ The fully developed branchiæ are obviously narrower than typical for the latter species. The lobes of the parapodia are in general similar though they do not become obvious so far forward. In the second division of the body the ventral lobe is similarly elongate and bifid at the tip with the inner or more dorsal lobe the longer; but the lobes are characteristically more divergent, thinner and more slender. The first bifid neuropodial lobes appear on the twenty-first setigerous segment. ”

“ Polychaetes with well-marked prostomium possessing tentacles and palps with evident and locomotor parapodia, supported (with few exceptions) by strong spines, the aciculi; muscular pharynx usually armed with jaws; septa and nephridia regularly metameric and similar throughout body; free living and predaceous. (2) Cryptocephala.—Tube-dwelling with body divided into thorax and abdomen marked by the setae, which are reversed in position in the neuropodium and notopodium respectively in the two regions. Parapodia hardly projecting ”

“ It seems probable that there are branchial plumes or filaments in some Arthropoda (some Crustacea) which can be identified with the distinct branchial organs of Chaetopoda, which lie dorsal of the parapodia and are not part of the parapodium. On the other hand, we cannot refuse to admit that any of the processes of an Arthropod parapodium may become modified as branchial organs, and that, as a rule, branchial out-growths are easily developed, de novo, in all the higher groups of animals. ”

“ The inferior setæ of the most anterior parapodia' much shorter than the dorsals, strongly curved. In the first notopodial fascia a much stouter, aciculiform, setæ which is uncate. Crochets with strongly narrowed neck; with two curved teeth at distal end above the beak which is decurved; in posterior region few in number, commonly four in a series. Anal cirri slender, filiform, much longer than the preceding branchiæ; one in the type has a short spur near its base. Total number of segments about one hundred and sixteen.
Length, 21.5 mm. ”

“ Setae always present and often very large, much varied in form and very numerous, borne by the dorsal and ventral parapodia (when present) . The prostomium and the segments generally often bear processes sensory and branchial. Eyes often present and comparatively complicated in structure. Clitellum not present as a definite organ, as in Oligochaeta. The anus is mostly terminal, and there are no anterior and posterior suckers. Nervous system often imbedded in the epidermis. Vascular system generally present forming a closed system of tubes. ”

“ Podmore advances the following theory in explanation of the phenomena of telepathy:
“If we leave fluids and radiant nerve-energy on one side, we find practically only one mode suggested for the telepathic transference—viz., that the physical changes which are the accompaniments of thought or sensation in the agent are transmitted from the brain as [Pg 26] undulations in the intervening medium, and thus excite corresponding changes in some other brain, without any other portion of the organism being necessarily implicated in the transmission. ”

“ To each division of the parapodium belongs typically a long tentacle, the cirrus, which may be defective upon one or other of the notopodium or neuropodium, and may be developed into an arborescent gill or into a flat scale-like process, the elytron (in Polynoe, &c.) ”

“ Consideration more or less adequate has now been given to the various phenomena in which there is proof apparent of the action of telepathy. The experimental evidence has shown that a simple sensation or idea may be transferred from one mind to another, and that this transference may take place alike in the normal state and in the hypnotic trance. It has been shown also that the transferred idea may be reproduced in the percipient's organism under various disguises; at one time, for instance, it may cause vague distress or terror, or a blind impulse to action ”

“ For on the view to which we are led by a review of all the evidence, a telepathic hallucination, like any other, is, as a rule, the work of the percipient's mind, and is not transferred ready made from the agent. As such it is frequently of slow growth, and there are grounds for believing that it is sometimes not externalised for the percipient's senses until some hours after the receipt of the original telepathic impulse. ”

“ In the two preceding chapters we have discussed experiments where the impression received by the percipient may be interpreted as having been a more or less accurate reproduction of the sensation experienced by the agent, or at most a translation of it into some other simple sensation. There have now to be considered various cases in which the transmission of thought is productive of other results in the percipient than the simple duplication or translation of a sensation. The most usual case is where the telepathic impulse leads to some action on the part of the percipient. ”

“ Perception is so largely a psychical process that it is difficult in any particular case to assign a definite value to the sensory element. And in a case of this kind, where, as appears to be generally the case with telepathic hallucinations, the vision is of brief duration, the difficulty is, of course, increased.
The hallucination in this, as in the previous case, occurred some hours before the death, and the evidential value of the coincidence is so far lessened. ”

“ But the whole discussion about the necessity of external excitation or of points de repère seems beside the mark in such cases as these. For there can be no question that what in the first instance excites the hallucination is not a present sensation, but a memory. Whether for the full development of a sensory hallucination some external stimulus to the sense-organ is necessary is here a question of quite minor importance. The really interesting fact in its bearing on the question of telepathic hallucination is that some hallucinations are shown to be centrally, not peripherally, initiated. ”

“ I call 'Ready?' The percipient says, 'Yes.' We have been drawing at the same time in different rooms. On returning to the study I compare the drawings and see with astonishment that Fräulein A. has drawn a serpent. Even the open mouth and the thickened end of the tail in the reproduction agree with the original. The experiment has succeeded in its essential part, and as regards strictness of conditions I think it quite unassailable. Unconscious suggestion is absolutely excluded, when agent and percipient are in different rooms. ”

“ Wherever the surface of the body is covered by pseudopodia, those processes, inasmuch as they have a power of spontaneous movement, enable the creatures possessing them slightly to aid or to resist the drifting action of the water in which they float.
But a living organism may be devoid of any definite shape whatever, as in Protamœba, [66] which consists of a mere particle of protoplasm, from which irregular-shaped processes of unequal size are irregularly protruded in every direction, so that the form of the creature may be said to be quite indeterminate. ”

“ But in the great majority of the cases there was no obvious antecedent to be discovered either in the condition of the percipient or in the surrounding circumstances, and we are led to the conclusion that an isolated hallucination of this kind is as little incompatible with ordinary health as a blush or a hiccough. At the same time we are entitled to infer, from the relatively large proportion of cases occurring when the percipient is in bed, or alone, that quiescence and freedom from external stimuli are favourable conditions for the genesis of [217] hallucinations. ”

“ That sleep, or rather the borderland which lies on either side of sleep, is peculiarly favourable to the production in the percipient, not only of hallucinations in general, but of telepathic hallucinations in particular, has already been shown. But the instances cited in the present chapter would seem to indicate that in the agent also sleep and trance (or possibly a trance self-induced in sleep or in waking) may facilitate such transmissions. ”

“ For this reason they are called false feet or pseudopodia. Nevertheless, by means of these pseudopodia the moners perform all the functions of the higher animals, moving them like real feet either to creep, climb, or swim. By means of these sticky threads they adhere to foreign bodies as with arms, and by shortening or elongating them they drag their own bodies after them. Each thread, like the whole body, is capable of being contracted, and every portion of it is as sensitive and excitable as the entire form. ”

“ Visions of this kind are of rare occurrence with waking percipients. The preoccupations of the daytime are probably in themselves sufficient to prevent the emergence of telepathic impressions under ordinary circumstances. But in the present instance it will be observed that the vision occurred in an interval of comparative rest after a period of active occupation. The feeling of gloom and depression mentioned by Mrs. Paquet may have marked the period of incubation, so to speak, of a latent impression of calamity. ”

“ To begin with, there is no sense-organ for our presumed new mode of sensation; nor at the present stage of physiological knowledge is there likelihood that we can annex any as yet unappropriated organ to register telepathic stimuli, as the semicircular canals are supposed to register the movements of the body in space. In lacking an elaborate machinery specially adapted for receiving its messages and concentrating them on the peripheral end of the nerves, telepathy would thus seem to be on a par with radiant energy affecting the general surface of the body. ”

“ The part played by coincident hallucination in the question of telepathy may be illustrated from another branch of scientific inquiry. For some years the "Germ Theory" rested mainly on observations of the distribution of certain diseases, their periodic character and their mode of propagation and development; phenomena which, though sufficiently striking, are not in themselves susceptible of exact interpretation. ”

“ In the result it [216] appeared that 1684 out of 17,000, or 9.9 per cent.—to wit, 655 out of 8372 men, and 1029 out of 8628 women—had experienced a sensory hallucination at some time in their lives. In about one-third of the cases the percipient had more than one experience of the kind. The phenomenon, therefore, though not so common as dreaming, is less rare than is generally supposed, seeing that about one in every ten educated persons has such an experience in the course of his life. ”

“ The latter term was proposed by Newman, under the form of propodeon, [411] and appears to be on the whole the most {492}suitable term for this part, which is of great importance in systematic entomology, owing to the extreme variety of characters it affords. Although it is clear that the propodeum is, in large part, an abdominal segment, yet its morphology is still uncertain; what parts are pleural, what tergal, and what may be chitinised spiracular area, or portions of the metathorax, being undetermined. ”