BYSSUMIA BYTTNERIA. 



657 



BYSSOMIA (Cuvier; SAXICAVA, Lamarck). 

 This genus, which Cuvier considered perfectly dis- 

 tinct from the genus Saxicava with regard to the 

 animal, differs but little as respects the shell, which 

 closely approximates to the genus Saxicava, of which 

 Lamarck makes it a species : it inhabits rocky fissures, 

 with the muscles and other shells attached by a byssus ; 

 but it is sometimes found buried in the sand, small 

 stones, and the roots of fuci, and even in the poly- 

 morphous Millepora, in which cases according to the 

 observations of Fabricius, it is divested of byssus. 

 The animal has its body more or less elongated, sub- 

 eylindrical, and prolonged backward by a tube bifur- 

 cated only at its extremity, there being an opening at 

 the lower and anterior part of the mantle, for the 

 passage of a small channelled foot, and for the byssus, 

 situated at the posterior base, and it has two powerful 

 adductor muscles. 



The shell is bivalve, often irregular, with a strong 

 epidermis, oblong, coarsely striated lengthwise, equi- 

 valve very inequilateral, obtuse, larger in front, and 

 as if rostrated at the back part ; the summits but 

 slightly marked, hinge without a tooth, or with only 

 the rudiment of one ; beneath the corslet a rather 

 long exterior ligament, and two distant rounded 

 muscular impressions. Only one species is known, 

 the Bysiiomya p/toladis, mentioned by Muller in his 

 Danish Zoology. 



BYSSUS. Several species of acephalous, or head- 

 less molluscs, produce an extremely fine kind of silky 

 filament, commonly called the beard ; it is similar to 

 that of insects, and employed by the animal to attach 

 itself to rocks or other objects, in such places as it 

 inhabits. It is formed by a conglomerate gland 

 placed near the foot, which latter part draws out the 

 silk from the excretory duct, and moulds it in a 

 groove on its surface. The muscle, perna, pinna, and 

 some other genera of molluscs, produce a byssus ; 

 the latter in such abundance that it is found in tufts 

 several inches long : in texture it closely resembles 

 raw spun silk, it is of a pale brown colour, and capa- 

 ble of being manufactured into articles of dress, such 

 as stockings and gloves, more however as objects of 

 curiosity than articles of commerce: of these, spe- 

 cimens are to be seen in the British, and other 

 museums. The configuration of many molluscs not 

 known to spin a byssus, appears to indicate its exist- 

 ence, and their local dwelling tends to confirm that 

 opinion ; but the impossibility of becoming intimate 

 with creatures we cannot study in their native 

 element, while they are in the full exercise of their 

 functions, renders it difficult in many cases for natu- 

 ralists to reason beyond analogy ; the best guide 

 perhaps that can be taken, though not always a safe 

 one to build a system upon, as the sports and freaks of 

 nature are so extraordinary, that they baffle the best 

 endeavours to reconcile them to oar understanding. 



That colossus of bivalves, the Tridacna gigas of 

 Lamarck, Chama gigas of Linnaeus, is said to affix 

 itself to rocks by a bundle of tendinous fibres, or 

 byssus, by which it remains suspended, notwithstand- 

 ing the magnitude of these shells, which sometimes 

 attain tho weight of 600 pounds, and measure several 

 feet in length : this assertion, and that of the force with 

 which the valves are closed, being able to snap a 

 ship's cable asunder, like many of the strange sights 

 travellers see, want additional confirmation to be 

 here given as established facts, though, reasoning by 

 analogy, no doubt might exist of the one or the other. 



NAT. HIST. VOL. I. 



A modern author, speaking of the byssus spun by 

 the common muscle, Mytilus cdidii, asserts that the 

 animal, when it has commenced " spinning its cable, 

 will make a trial of its strength by drawing it strongly 

 towards her, before she proceeds to stretch out a 

 second, and these cords, which she spins with so 

 much art, are in reality as serviceable to them as 

 cables are to a ship." He adds, that there are " fre- 

 quently 150 of those little cables employed in moor- 

 ing a muscle, each cable scarcely two inches lon." 



The writer of this article has patiently observed 

 the habits of muscles for days together, in situations 

 favourable to their growth, and never could witness 

 the animal in the act of spinning its miniature cables, 

 much less observe that spider-like kind of wisdom, of 

 trying their strength when produced. He made 

 numberless experiments to enable him to do so, all 

 ending in the fact, that these animals do moor them- 

 selves to various submarine bodies by their silken 

 threads, under peculiar circumstances of situation, 

 often in groups suspended to each other, generally in 

 beds or strata, and sometimes, but very rarely, single 

 individuals were seen attached to stones or other 

 matter, not moveable by the action of the tide ; but 

 when or how this operation was effected, the writer 

 never could ascertain, from the most minute ocular 

 examination. With regard to the length of the thread.*, 

 they varied from one-tenth to two inches and a half, 

 but they never appear disposed with any appearance 

 of regularity or order, as to purpose, beyond that of 

 meeting with any object in its vicinity. The num- 

 bers of these threads frequently exceeded one hundred, 

 and when all but a few were separated or removed 

 from the mollusk, no attempt was made to renew 

 them in the same or any other direction ; but when a 

 number of individuals were carefully wiped, and freed 

 entirely from every appearance of byssus, they all 

 shortly spun threads attached to the nearest object, 

 whether each other or not, indicating a consciousness 

 of their utility, without exhibiting any other of those 

 instinctive habits, more peculiarly observable in some 

 of the spinning animals, and another proof, were it 

 requisite, of the difficulty of ascertaining where 

 ; instinct ends, or reason commences. 



The fine linen called, in Greek, byssus, mentioned 

 j in sacred writing, of which the costly sacerdotal gar- 

 J ments were made, is supposed by some commentators 

 , to have been fabricated from the silken produce of 

 j the pinna ; but as its brilliant white hue is so highly 

 ! praised, it was more probably made from asbestos, the 

 j art of weaving which was well known to the ancients, 

 i and cloth of it was used to preserve the ashes of princes 

 I and heroes from becoming mingled with the more 

 ignoble dust of the woods and rare spices whose 

 aromatic flames consumed thoir mortal remains. 



BYSTROPOGON (Le Heritier). The name 

 signifies close throated, as applied to the tube of the 

 flower. It is a genus comprising four species of 

 green-house under-shrubs, natives of the Canary 

 Islands. They belong to the natural order Labiates, 

 and are plants of no great beauty. 



BYTTNERIA (Loeffling). A genus of shrubs, 

 under-shrubs, and herbs, natives of many of the 

 warmer parts of the world. They bear pentandrious 

 flowers, and give name to an order of the natural 

 system, viz. Byttneriaceee. The generic character, 

 according to Loeffling, is calyx five-parted ; petals 

 clawed, cupped at top, or eared, ligulated at the 

 back; tube pitcher-shaped, bearing the stamens, 

 3 C 



