Jelly-fish, Star-fish and Sea-urchins: Being a Research on Primitive Nervous SystemsK. Paul, Trench & Company, 1885 - 323 páginas "Among the most beautiful, as well as the most common, of the marine animals which are to be met with upon our coasts are the jelly-fish and the starfish. Scarcely any one is so devoid of the instincts either of the artist or of the naturalist as not to have watched these animals with blended emotions of the aesthetic and the scientific--feeling the beauty while wondering at the organization. How many of us who live for most of the year in the fog and dust of large towns enjoy with the greater zest our summer's holiday at the seaside? And in the memories of most of us is there not associated with the picture of breaking waves and sea-birds floating indifferently in the blue sky or on the water still more blue, the thoughts of many a ramble among the weedy rocks and living pools, where for the time being we all become naturalists, and where those who least know what they are likely to find in their search are most likely to approach the keen happiness of childhood? If so, the image of the red sea-stars bespangling a mile of shining sand, or decorating the darkness of a thousand grottoes, must be joined with the image, no less vivid, of those crystal globes pulsating with life and gleaming with all the colours of the rainbow, which are perhaps the most strange, and certainly in my estimation the most delicately lovely creatures in the world"--Introduction. (PsycINFO Database Record (c) 2010 APA, all rights reserved). |
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able ambulacral feet artificial rhythm Aurelia aurita become bell blocked brium cause ceased chloroform co-ordination continue contractile strip contractile tissues contraction contraction-waves covered-eyed Medusa crawling curare diastole direction discharge Echinoderm Echinodermata Echinus effect excising excitable tissues experiments fact feeble fibres forceps fresh water function ganglionic glycerine hour induction shocks influence instance intervals irritability latter lithocyst locomotor centres manubrium marginal bodies marginal ganglia minutes movements muscle muscular mutilated naked-eyed Medusa natural rhythm nectocalyx nerve nerve-cells nerve-centre nerve-fibres nerve-ring nerve-trunks nervous network nervous system normal sea-water observed occur organ paralyzed pass pedicellariæ pedicels period of latent physiological plexus poison portion prepotent pulsations radial tubes rays reflex reflex action removed response result rhythmic action round Sarsia seconds segments spasm species specimens spines spontaneity Star-fish strychnia suckers surface swimming motions swimming-bell systole tank temperature tentacles tentacular tetanus Tiaropsis indicans tion umbrella unmutilated animal wave whole
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Página 253 - If an animal so exceedingly intolerant of fresh water as is a marine jelly-fish may yet have all its tissues changed so as to adapt them to] thrive in fresh water, and even die after an exposure of one minute to their ancestral element, assuredly we can see no reason why any animal in earth or sea or anywhere else may not in time become fitted to change its element.
Página 24 - ... fibre, it contracts on receiving this stimulus. I may add that when nerve-cells are collected into ganglia, they often appear to discharge their energy spontaneously ; so that in all but the very lowest animals, whenever we see apparently spontaneous action, we infer that ganglia are probably present.
Página 25 - I here draw between muscle and nerve. A stimulus applied to a nerveless muscle can only course through the muscle by giving rise to a visible wave of contraction, which spreads in all directions from the seat of stimulation as from a centre. A nerve, on the other hand, conducts the stimulus without undergoing any change of shape. Now in order not to forget this...
Página 321 - ... unicellular • organisms, but with animals of more complex structure. Romanes and Loeb have studied the radiates. Romanes attributes sense consciousness both to jelly-fish and to starfish, but he reaches this conclusion from the disputed standpoint of the continuity hypothesis. " The starfish," he says, " perceived the proximity of food, as shown by their immediately crawling towards it*.
Página 252 - ... immersion in a saturated solution of salt. While in such a solution they are motionless, with manubrium and tentacles relaxed, so resembling the freshwater Medusa shortly after being immersed in a mixture of i part sea water to 5 of fresh ; but there is the great difference that while this small amount of salt is very quickly fatal to the fresh-water species, the large addition of salt exerts no permanently deleterious influence on the marine species. We have thus altogether a curious set of...
Página 285 - In climbing perpendicular or inclined surfaces of rock covered with waving sea- weeds, it must be no small advantage to an echinus to be provided on all sides with a multitude of forceps adapted...
Página 25 - I may add, from protoplasm — by displaying the property of conducting invisible or molecular waves of stimulation from one part of an organism to another — so establishing physiological continuity between such parts without the necessary passage of contractile waves.
Página 301 - ... so completely destroying physiological continuity in the rows of ambulacral feet and muscular system of the animal, does not destroy physiological continuity in the external nerve-plexus ; for however much the nerve-ring and nerve-trunks may be injured, stimulation of the dorsal surface of the animal throws all the ambulacral feet and all the muscular system of the rays into active movement. This fact proves that the ambulacral feet and the muscles are all held in nervous connection with one...
Página 39 - If the animal is vigorous, the eflect of a momentary flash thrown upon it during one of the natural pauses is immediately to originate a bout of swimming ; but if the animal is non-vigorous, it usually gives only one contraction in response to every flash. That it is light per se, and not the sudden transition from darkness to light, which here acts as the stimulus, is proved by the result of the converse experiment — viz. placing a vigorous specimen in sunlight, waiting till the middle...