How Are Pearls Made Naturally

How are pearls made naturally as recorded by George Kunz and Charles Stevenson in 1908.
How are pearls made naturally remained a mystery for millenniums. Only in the last few centuries has man been able to deduct how these amazing gems occur naturally in the lowliest of earth creatures.

Ironic, isn't it? How a lowly beast could make a thing of such worth, value and beauty....a lesson to us all...out of earth we were created and in the same way great things can blossom out of the most difficult situations!

On this page, George Kunz, the famous pearl expert of the turn of the twentieth century, writes in 1908, the following detailed research available at his time about the understanding of how are pearls made naturally. I hope you enjoy his efforts to inform us of the current understanding of his day.

How are pearls made naturally?

Naturalists generally accepted the answer to the question: how are pearls made naturally, in that pearls originate in pathological secretion formed, either as the result of the intrusion of hard substances, or by the encysting or covering of ova or other objects of internal origin; and there was no important cleavage of opinion of how are pearls made naturally until the development of the parasitic theory, as a result of the researches of the Italian naturalist Filippi, and those following his line of investigations. This theory is not severely in conflict with those of Reaumur, Linnaeus, Home, etc, but relates principally to the identity of the irritating or stimulating substance which forms the nucleus of the pearl.

How are pearls made naturally? Filippi's Obervations.

In examining a species of fresh-water mussel, the Anodonta cygnea, occurring in ponds near Turin, and especially the many small pearly formations therein, Filippi observed that these were associated wit the presence of a trematode or parasitic worm, which he named Distomum duplicatum, and which appears to be closely allied to the parasite which causes the fatal "rot" or distemper in sheep. Under the microscope, the smallest and presumably the youngest of these pearls showed organic nuclei which appeared undoubtedly to be the remnants of the trematode. In Anodonta from other regions, which were not infested with the ditoma, pearls were very rarely found by Filippi. In a paper, published in 1852, containing a summary of his observations, he concluded that a leading, if not the principal, cause of pearl-formation in those mussels was the parasite above noted; and in later papers he included such other forms as Atax ypsilophorus within the list of parasitic agencies which might excite the pearl-forming secretion, comparing their action to that of the formation of plant-galls.

How are pearls made naturally? Kuchenmeister, Movius, Kelaart Research.

The discovery of the parasitic origin of pearls was extended to the pearl-oysters and to other parasites by Kuchenmeister in 1856, by Movius in 1857, and by several other investigators. Prominent among these were E. F. Kelaart and his assistant Humbert, who, in 1859 disclosed the important relation which the presence of vermean parasites bears the origin of pearls in the Ceylon oysters. These naturalists found "in addition to the Filaria and Cercaria, three other parasitical worms infesting the viscera and other parts of the pearl-oyster. We both agree that these worms play an important part in the formation of pearls." Dr. Kelaart likewise found eggs from the ovarium of the oyster coated with nacre and forming pearls, and also suggested that the silicious internal skeletons of microscopic diatoms might possibly permeate the mantle and become the nuclei of pearls. Unfortunately, Dr. Kelaart's investigations were terminated by his death a few months thereafter.

How are pearls made naturally? Garner, Giard, and Dubois Confirmations.

In 1871, Garner ascribed the occurrence of pearls in the common English mussel (Mytilus edulis) to the presence of distomid larvae. Giard, and other French zoologists, made similar discoveries in the case of Donax and some other bivalves. In 1901, Raphael Dubois confirmed the observations of Garner, associating the production of pearls in the edible mussels on the French coasts with the presence of larvae of a parasite, to which he gave the name of Distomum margaritarum, and boldly announced: "La plus gelle perle n'est donc, en definitive, que le brilliant sarcophage d'un ver." or in English: "The most beautiful pearl is only the brilliant sarcophagus of a worm."

How are pearls made naturally? Jameson's Disclosure

Prof. H. L. Jameson, in 1902, disclosed the relation which exists between pearls in English mussels (Mytilus) and the larvae of Distomum somateriae. The life history of this trematode, as revealed by Dr. Jameson, is especially interesting from a biological standpoint, since it is entertained by three hosts at different times: the first host is a member of the duck family; the second is the Tapes clam (Tapes decussatus), or perhaps the common cockle (Cardium edule), which incloses the first larval stage, and the third is the edible mussel, in which the second larval stage of the parasite stimulates the formation of pearls. At the Brighton Aquarium and the Fish Hatchery at Kiel, Dr. Jameson claims to have succeeded in artificially inoculating perfectly healthy mussels with these parasites by associating them with infested mollusks, and thereby producing small pearls.

From Dr. Jameson's interesting paper we abridge the following account of the manner in which the pearls are developed. The trematode enters Mytilus edulis as a tailless cercaria, and at first may often be found between the mantle and shell. The larvae, after a while, enter the connective tissue of the mantle, where they come to rest, assuming a spherical form, visible to the naked eye as little yellowish spots about one half millimeter in diameter. At first the worm occupies only a space lined by connective-tissue fibrils, but soon the tissues of the host give rise to an epithelial layer, which lines the space and ultimately becomes the pearl-sac. If the trematode larva completes its maximum possible term of life, it dies, and the tissues of the body break down to form a structureless mass which retains the form of the parasite, owning to the rigid cuticle. In this mass arise one or more centers of calcification, and the precipitation of carbonate of lime goes on until the whole larva is converted into a nodule with calcospheritic structure. The granular matter surrounding the worm, if present, also undergoes calcification. The epithelium of the sac then begins to shed a cuticle of conchiolin, and from this point the growth of the pearl probably takes place on the same lines and at the same rate as the thickening of the shell.

How are pearls made naturally? Dubois' Experiments

Fully as remarkable as the observations of Dr. Jameson are the results claimed by Professor Dubois in experimenting with a species of pear-oyster (M. vulgaris) from the Gulf of Gabes on the coast of Tunis, where they are almost devoid of pearls, a thousand or more shells yielding on an average only one pearl. Conveying these to the coast of France in 1903, he there associated them with a species of trematode-invested mussel (Mytilus gallo-provincialis), and after a short period they became so infested that every three oysters yielded and average of two pearls. This claim has not been without criticism; but who ever knew scientists to agree?

How are pearls made naturally? Seurat Findings

In the pearl-oyster of the Gambier Island (M. margaritifera cumingi), Dr. L. G. Seurat found that the origin of pearls was due to irritation caused by the embryo of a worm of the genus Tylocephalum, the life of which is completed in the eagle-ray, a fish which feeds on the pearl-oyster.

How are pearls made naturally? Herdman and Hornell's Discoveries

In 1903, Prof. W. A. Herdman, who, at the instance of the colonial government, and with the assistance of Mr. James Hornell, examined the pearl-oyster resources of Ceylon, announced: "We have found, as Kelaart did, that in the Ceylon pearl-oyster there are several different kinds of worms commonly occurring as parasites, and we shall, I think be able to show that Cestodes, Trematodes, and Nematodes may all be concerned in pearl-formation. Unlike the case of the European mussels, however, we find that in Ceylon the most important cause is a larval Cestode of the Tetrarhynchus form."

How are pearls made naturally? More by Hornell

In his investigation of the Placuna oyster in 1905, Mr. James Hornell found that the origin of pearls was due to minute larva of the same stage and species as that which caused he pearls in the Gulf of Manar oyster.

The spherical larvae of this tapeworm sometimes occur in great abundance, and there is evidence of forty having been found in a single pearl oyster. Mr. Hornell states that the living worm does not induce pearl-formation, this occurring only when death overtakes it while in certain parts of the oyster. As a consequence, pearls are more numerous in oysters which have been long infected, where the worms are older and more liable to die. This parasitic worm has been traced from the pearl-oyster to the trigger-fishes, which eat the pearl-oysters and thence into certain large fish-eating rays, where is becomes sexually mature and produces embryos which enter the pearl-oyster and begin a new cycle of life-phases.

How are pearls formed naturally? Variations

While the theory that pearls are caused by the intrusion of some unusual substance has the evidence of actual demonstration in many instances, and is unquestionably true to a large extent, yet microscopic examination of some pearls suggests the theory that a foreign substance is not always essential to their formation, and that they may originate in calcareous concretions of minute size termed "calcospherules."

How are pearls made naturally? 3 Classifications of Pearls

As regards their origin, Professor Herdman classifies pearls into three sorts: (1) "Ampullar pearls," which are not formed within closed sacs of the shell-secreting epithelium like the others, but lie in pockets or ampullae of the epidermis. The nuclei may be sand-grains or any other foreign particles introduced through breaking or perforation of the shell. (2) "Muscle pearls," which are analogous to gallstones, formed around calcospherules at or near the insertion of the muscles. And (3) "Cyst pearls," in which concentric layers of nacre are deposited on cysts containing parasitic worms in the connective tissue of the mantle and within the soft tissues of the body.

How are pearls made naturally? Further Illustrations

Even a particle of earth, clay, or mud may form the nucleus of a pearl. This was illustrated a few years ago in a fine button-shaped pearl, which was accidentally broken under normal usage and was found to consist of a hard lump of white clay surrounded by a relatively thin coating of nacre. More remarkable yet are the cases in which a minute fish, a crayfish, or the frustule of a diatom has formed the nucleus.

How are pearls made naturally? More Instances

Several instances have been described by Woodward, Gunther, Putnam, Stearns, and others, where small fish have penetrated between the mantle and the shell of the mollusk, and the latter has resented the intrusion by covering the intruder with a pearly coating. In two or three instances the secretion occurred in so short a time that the fish suffered no appreciable decomposition, and its species is readily identified by observation through the nacreous layer.

How are pearls made naturally? Remarkable Specimens

Among the remarkable specimens of this nature which have come under our observations are two very curious shells received in March, 1907, from the Mexican fisheries. One of these specimens shows an encysted fish, so quickly covered and so perfectly preserved that even the scales and small bones are in evidence; indeed, one can almost detect the gloss on the scales of the fish; and in the other--with remarkable comet-like appearance--a piece of ribbed seaweed is apparently the object covered.

Early Theories of how pearls were made.

How are pearls made naturally?

How are pearls made? Theories by Schroeter.

How are pearls made? Theories by Dall.

How are pearls made? Theories by Woodward.

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