These are known as olfactory filaments or aesthetascs.
One osphradium or branchial olfactory organ is usually present on each side, on either side of the anus on the inner wall of the mantle, near the base of the last gill.
Beneath the ciliated groove is placed an elongated ganglion (olfactory ganglion) connected by a nerve to the supraintestinal (therefore the primitively dextral) ganglion of the long h, k, m, Stomach.
In front, near the anterior attachment of the gill-plume, is the osphradium (olfactory organ) dis h covered by J.
The osphradium (olfactory organ of Spengel).
It is said that 13,000 such olfactory organs are present on the feeler of a wasp, and 40,000 on the complex antennae of a male cockchafer.
In addition to the eyes and the olfactory circle on the head scattered tactile papillae are found on the ectoderm.
Each of the visceral ganglia is connected or combined with an olfactory ganglion underlying an area of specialized epithelium, which constitutes the olfactory organ, the osphradium.
The olfactory perceptive membrane is restricted to the posterior innermost region of the nasal chamber, where it covers a slight bulging-out prominence on the nasal wall.
It will be remembered that, according to Spengel, the osphradium of mollusca is definitely and intimately related to the gill-plume or ctenidium, being always placed near the base of that organ; further, Spengel has shown that the nerve-supply of this olfactory organ is always derived from the visceral loop. Accord ingly, the nerve-supply FIG.
Sp, Abdominal ganglion which represents also the supra-intestinal ganglion of Streptoneura and gives off the nerve to the osphradium (olfactory organ) o, and another to an unlettered socalled " genital " ganglion.
One of the most puzzling features in its structure, and, at the same time, one of the greatest obstacles to the view that it is essentially primitive and not merely a degenerate creature, is the entire absence of the paired organs of special sense, olfactory, optic and auditory, which are so characteristic of the higher vertebrates.
A radial vertical plane so as B, Inferior or adoral olfactory to pass through the long axis of_the tentaculocyst.
The hemispheres are rather elongated and subcylindrical, the olfactory lobes are large and project freely in front of the' hemispheres, and the greater part of the cerebellum is uncovered.
Nr, Olfactory nerve.
9, 10) of _ the nervous systems of ` Patella and of Haliotis, e as determined by Spengel, show the identity in the origin of the nerves passing from the visceral loop to Spengel's olfactory ganglion of the fig..
Limpet, and that of the g ' nerves which pass from the visceral loop of Haliotis to the olfactory patch or osphradium, which lies in immediate relation on the right and on the left side to the right and left gill-plumes (ctenidia) respectively.
O, o, Right and left olfactory ce.pl, The cerebro-pleural conganglia and osphradia re nective.
Spengel showed that the parabranchia of Gastropods is the typical olfactory organ or osphradium in a highly developed condition.
The Heteropoda are further remarkable for the high development of their cephalic eyes, and for the typical character of their osphradium (Spengel's olfactory organ).
On account of the shortness of the visceral loop and the proximity of the right visceral ganglion to the oesophageal nerve-ring, the nerve to the osphradium and olfactory ganglion is very long.
Krohn posite to it is the visceral ganglion of in Marsenia =Echino- the right side, which gives off the long spira) there may be a nerve to the olfactory ganglion and break at a later stage, osphradium o.
The nautiloid shell In Planorbis and in Auricula (Pulmonata, formed on the larva allied to Limnaeus) the olfactory organ is being cast, and a new on the left side and receives its nerve from shell of a different form the left visceral:ganglion.
In their simpler condition they are long and many-jointed, the segments bearing numerous olfactory and tactile nerve-endings.
A pair of eyes lie dorsally and behind them is a b closed circlet, often pulled out into various shapes, of modified epidermis, to which an olfactory function has been attributed.
138) imagined it merely "to contain an infinity of nerves, disposed like net-work, all of which lead immediately to the nostrils," and add to the olfactory faculty.
The regions of the cortex, whose conduction paths are early completed, may be arranged in groups by their connexions with sense-organs: eye-region, ear-region, skin and somaesthetic region, olfactory and taste region.
Von Kdlliker's olfactory pit.
A, Superior or aboral olfactory A, Superior or aboral olfactory ML, Marginal lappets.
When specialized as bearers of sensory (olfactory or tactile) organs, the rami are generally elongated, many-jointed and flagelliform.
In the great majority of Crustacea the antennules are purely sensory in function and carry numerous " olfactory " hairs.
Its physiological effects are much more persistent and injurious than sulphuretted hydrogen, producing temporary paralysis of the olfactory nerves and inflammation of the mucous membrane.
Owing to the small size of the olfactory lobes the anterior arms of the latter commissure are wanting.
The olfactory organ is poorly developed, and it is still a question whether birds possess much power of smell; many are certainly devoid of it.
In cormorants (Phalacrocoracidae), and especially in Sula, where the nasal slits become completely closed up, and the greater portion of the nasal cavity is also abolished, being restricted to the olfactory region with its unusually wide choanae.
R, Olfactory organ.
C, Olfactory (osphradial) ganglionpair.
1, Exit of olfactory nerve.
These segments are abundantly supplied with elongate tooth-like projections connected with nerve-endings probably olfactory in function.
- A, Section in a plane vertical to the surface of the neck of Patella through a, the rudimentary ctenidium (Lankester's organ), and b, the olfactory epithelium (osphradium); c, the olfactory (osphradial) ganglion.
Pericardium, and is therefore a typical o, Olfactory ganglion, nephridium, was not known.
Dium or olfactory Yet in some Pectinibranchia (Paludina) organ).
43) shows the nerve connecting this abdomino-visceral ganglion with the olfactory ganglion of Spengel.
Left olfactory ganglion (parieto-splanch nic).