BIVALVE MOLLUSCANS. 261 



differently constructed and proceed in a different 

 manner. 



We next come to those bivalves which fix 

 themselves to the rocks, or in other secure 

 stations, by means of a Byssus, which is usually 

 formed of brown silken threads, intertwined like 

 wool, spun from the foot of the animal, formed 

 from a slimy fluid furnished by a gland situated 

 under its base. Poli says, with respect to the 

 byssus of muscles, which have all of them this 

 faculty, that it is of the same structure with hair, 

 and that, at the extremities, it is furnished with 

 little cups or suckers, by which it adheres so 

 firmly, that the muscles can only be drawn from 

 the water in great bunches. Some species are 

 entirely enveloped with this substance. These 

 provisions evidently indicate design and Creative 

 Wisdom. 



The giant Clamp-shells 1 belonging to the bi- 

 muscular section, sometimes four feet in length 

 and weighing more than five hundred pounds, 

 suspend their vast bulk by means of a strong 

 byssus : below the hinge is a large opening, 

 through which the animal passes a bundle of 

 tendinous fibres, by which it is suspended to the 

 rocks however large and weighty its shells, and 

 thus it is enabled to fix itself securely, wherever 

 its instinct directs it. 



1 Tridacne Gig as. 



