How to use Sense-organs in a sentence
The ectoderm furnishes the general epithelial covering of the body, and the muscular tissue, nervous system and sense-organs.
The sense-cells form, in the first place, a diffuse system of scattered sensory cells, as in the polyp, developed chiefly on the manubrium, the tentacles and the margin of the umbrella, where they form a sensory ciliated epithelium covering the nerve-centres; in the second place, the sense-cells are concentrated to form definite sense-organs, situated always at the margin of the umbrella, hence often termed " marginal bodies."
In Hydromedusae the sense-organs are always exposed at the umbrellar margin (hence Gymnophthalmata), while in Scyphomedusae they are covered over by flaps of the umbrellar margin (hence Steganophthalmata).
Here the medusoid, attached by the centre of its ex-umbral surface, has lost its velum and sub-umbral muscles, its sense organs and mouth, though still retaining rudimentary tentacles.
When fully developed the medusa is characterized by the sense organs being composed entirely of ectoderm, developed independently of the tentacles, and innervated from the sub-umbral nerve-ring.Advertisement
The sense organs are typically ocelli, never otocysts.
The characteristic sense-organs are ectodermal otocysts, absent, however, in some genera, in which case cordyli may replace them.
The manubrium bearing the gonads is mouthless, and the umbrella is without tentacles, sense-organs, velum or radial canals.
Medusae with sense-organs represented by otocysts derived from modified tentacles (tentaculocysts), containing otoliths of endodermal origin, and innervated from the ex-umbral nerve-ring.
The sense-organs are tentaculocysts which are usually enclosed in vesicles and may be sunk far below the surface.Advertisement
Both these medusae have sense-organs of a peculiar type, which are said to contain an endodermal axis like the sense-organs of Trachylinae, but the fact has recently been called in question for FIG.
Their sense-organs require renewed investigations.
In this matter, differentiation has proceeded very differently in animals and plants respectively, no nerves or sense organs being structurally recognizable.
Even the root tip, which shows a certain differentiation into root cap and root apex, cannot be said to be a definite sense organ in the same way as the sense organs of an animal.
We have spoken of the absence of structural differentiation in the sense organs.Advertisement
The nervous system and sense organs are highly developed.
With respect to the sense organs of the Nemertines, we find that eyes are of rather constant occurrence, although many Heteronemertines living in the mud appear to be blind.
There are no specialized sense-organs or vascular or respiratory systems. There is a wide body-cavity, but as this has no connexion with the renal or reproductive organs it cannot be regarded as a coelom, but probably is a blood-space or haemocoel.
Some scattered papillae may possibly be sense-organs.
The larval forms are provided with eye-spots, but no very specialized sense organs are found in the adult.Advertisement
Sense-organs in a similar position were discovered in Limulus by Patten (42) in 1894.
The sense-organs are highly developed; the wing-membranes are exceedingly sensitive; the nose-leaf is also an organ of perception, and the external ear is specially modified to receive soundwaves.
Reflection shows that our apprehension of the tree is conditioned by the sense-organs with which we have been endowed, and that the apprehension of a blind man, and still more the apprehension of a dog or horse, is quite different from ours.
The only sense organs described are eyes, which occur in some species, and may number one to four pairs.
In addition to the tentacles, the margin of the umbrella bears sense-organs, which may be of several kinds and may attain a high degree of complexity.Advertisement
The sense-organs are always situated at the margin of the unbrella and may be distinguished from the morphological point of view into two categories, according as they are, or are not, derived from modifications of tentacles; in the former case they are termed tentaculocysts.
The sense organs are eyes, antennae, sensory styles and a statocyst in a few species.
United with these ganglia on the outer sides are the osphradial ganglia, above which the epithelium is modified to form a pair of sense-organs, corresponding to the osphradia of other Molluscs.
At the anterior end the head is differentiated; it bears the sense-organs, and contains the muscular pharynx within which is the radular apparatus.
The special sense-organs are a pair of eyes on the head, a pair of otocysts or statocysts, and a pair of osphradia which have already been mentioned.Advertisement
One end of the body, through contact, during locomotion, with fresh tracts of medium and other forms of stimuli, has become more specialized than the rest, and here the nervous system and sense-organs are more densely aggregated than elsewhere, forming a means of controlling locomotion and of correlating the activities of the inner organs with the varying stimuli that impinge upon the body.
The Turbellaria undoubtedly form the most primitive division, as is shown by their free-living habits, ciliation and sense-organs.
He holds indeed that, in accordance with the law of substance, consciousness must be evolved from unconsciousness with the development of sense organs and a central nervous organ.
These papillae form pallial sense-organs, I containing nerve-end bulbs, covered by a dome of cuticle, and innervated from the pallial nervecords.
The sense organs of the shell-valves have already been described.Advertisement
With regard to sense organs the epithelial papillae of the mantle have been mentioned.
The tactual organs of the soles, and the muscular sense organs of limbs and trunk, are originating perceptions that indicate that the self is standing on the solid earth, yet the eyes are at the same time originating perceptions that indicate that the solid earth is far away below the standing self.
With certain of these it stands associated most closely, namely, with the vestibular, representing the sense organs which furnish data for appreciation of positions and movements of the head, and with the channels, conveying centripetal impressions from the apparatus of skeletal movement.
The sense-organs are covered over by flaps of the umbrellar margin (hence " Steganophthalmata "), and are always tentaculocysts, that is to say, reduced and modified tentacles, which bear usually both ocelli and otocysts, and are hollow.
In these medusae, however, the central nervous system does not form continuous rings, but occurs as four or eight separate con centrations at the margin of the umbrella, centred each round one of the sense-organs (tentaculocysts).Advertisement
The sense-organs of the Scyphomedusae are on the whole of a very uniform type.
The only certain criterion of a medusa-individual is the presence of definite sense-organs, but in cases where the organism is much reduced, this criterion may fail us, as it does in the genus Lucernaria.
Nevertheless a comparison between Lucernaria and its close ally Haliclystus shows clearly that the absence of sense-organs in the former is the result of secondary reduction, so that a true medusa may lose its most characteristic feature.
Hence the absence of sense-organs in the scyphistoma does not necessarily disprove its medusoid character, while its anatomical structure resembles that of a simple scyphomedusa, such as Lucernaria, rather than that of a polyp.
The only other sense-organs are the captacula, which are tactile and olfactory.Advertisement
Beyond the parapodia are four pairs of organs, often called suckers, but probably of sensory nature, and comparable to the lateral sense organs of Capitellids (Wheeler).
Skeletal appendages are spines (radioles), pedicellariae, and, in some forms, minute sense-organs called sphaeridia.
In regard to sense-organs, ophthalmoscopic observations on the eyes of living mammals (other than man) have revealed the existence of great variation in the arrangement of the bloodvessels, as well as in the colour of the retina; blue and violet seem to be unknown, while red, yellow and green form the predominating shades.
These are acute sense organs which can detect female pheromones on the air from astonishing distances.
Look at the different sense organs among different animals and compare them.Advertisement
The sense-organs may be tentaculocysts, i.e..
As has been described above, the endoderm may also contribute to the sense-organs, but such contributions are always of an accessory nature, for instance, concrement-cells in the otocysts, pigment in the ocelli, and never of sensory nature, sense-cells being Hydromedusae are of separate sexes, the only known exception being Amphogona apsteini, one of the Trachomedusae (Browne ).
The simple nerve-ganglion or brain (g) lies on the anterodorsal side of the pharynx, and by its position determines the orientation of the animal, the cloacal opening lying on the same side, and the course of the gut being" neural."The sense organs are a pair of pigmented eyes (oc), and two pairs of antennae, one anterior proximal and near the wreath, the other distal and usually more or less lateral.
Riding in a car, being on a ship, or taking an amusement park ride can cause conflicting stimulation of the different sense organs.
First, the ectoderm cells will develop into sense organs and the nervous system.