Joseph Thomas Cunningham

Name: Encyclopædia Britannica, Ninth Edition
Author: Joseph Thomas Cunningham

Encyclopædia Britannica, Ninth Edition (1888)

Summary

“Encyclopædia Britannica, Ninth Edition”, published in 1888, is a work by Joseph Thomas Cunningham. It explores elements such as Teredo, burrow and posterior adductor.

Quotes from Encyclopædia Britannica, Ninth Edition (Joseph Thomas Cunningham)

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ When a knot or nail or the tube of a neighbour is reached, the course of the burrow is altered so as to bend round the obstruction. One burrow is never found to break into another.
The adult Teredo, when removed from its burrow and calcareous tube, is from a few inches to 3 feet in length, according to the species to which it belongs, and is cylindrical and worm- like in appearance. The anterior end, which lies at the bottom of the burrow, is somewhat enlarged and bears a pair of shells or valves, which are not connected by the usual ligament, but are widely separated dorsally. ”

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Source: Wikisource

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ By the growth of a preoral lobe provided with a ring of cilia, and by the formation of a mouth and an anus, the trochosphere stage is reached. A pair of thin shells then appear on the sides of the larva, connected by a hinge on the dorsal median line, and the foot grows out between mouth and anus. ”

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Source: Wikisource

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ At the same time it is difficult to explain how the soft muscular foot can penetrate into hard wood. The process is of course slow, and Jeffreys supposes that particles are detached one by one from the moistened surface to which the foot is applied. In any case the valves are covered by an epidermis, which could scarcely be there if they were used in burrowing.
Teredo grows and burrows at an extremely rapid rate: spawning takes place in the spring and summer, and before the end of the year the animals are adult and their burrows of large size. ”

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Source: Wikisource

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ The valves are triangular in shape and very concave on the side which is in contact with the animal. In front their edges are widely separated, and the mantle tube, which is elsewhere closed, has here a slight median aperture, through which the short sucker-like foot can be protruded. The next portion of the body behind the shell-bearing part is naked, except for the shelly lining of the burrow, which is secreted by this part. ”

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Source: Wikisource

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ The heart is above the intestine and not perforated by it. The two valves are connected by an anterior adductor muscle.
From its resemblance to Pholas, Teredo is placed by conchologists in the family Pholadidæ, among the Isomya; but it is still undecided which part of the body corresponds to the posterior adductor. According to Quatrefages, it is a muscular band passing transversely between the handles of the pallets. His discussion of this point is connected with another, namely, the nature of the long tubular portion of the body behind the valves. ”

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Source: Wikisource

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ Behind the pallets the tubular body bifurcates, forming two siphons similar to those of other Lamellibranchs; the siphons can be contracted or expanded within wide limits of length. The principal organs of the body—stomach, heart, generative organs, and nephridia—are situated in the anterior part of the body, forming a visceral mass, which extends some distance behind the valves. ”

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Source: Wikisource

Joseph Thomas Cunningham, Encyclopædia Britannica, Ninth Edition (1888)

“ Besides the visceral ganglia a cerebral and a pedal pair are present. The stomach is provided with a large crystalline style. The function of the pallets is to form an operculum to the calcareous tube when the siphons are withdrawn into it. In some species the external or narrower end of the calcareous tube is provided with transverse laminae projecting into the lumen; and in some the external aperture is divided by a horizontal partition into two, one for each siphon.
The Teredo, according to Quatrefages, is diœcious, though Gwyn Jeffreys believes it to be hermaphrodite. ”

Joseph Thomas Cunningham

Summary

Quotes from Encyclopædia Britannica, Ninth Edition (Joseph Thomas Cunningham)

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