352 Natural Histoiy of Molluscous Animals : — 



ture. They are affixed in various ways ; for the Author of 

 nature^ in accomplishing one and the same end, ever varies 

 his means and workings. The oysters and iSpondyli, horrid 

 with projecting spines, adhere by cementation, that is, without 

 the medium of any connecting membrane or ligament ; the 

 inferior valve, in its growth, becoming fixed and modelled to 

 the foreign substance on which it lies. The Anomige, which 

 in character much resemble the oysters, are fixed partly in 

 the same way, but their chief hold is effected by the transverse 

 muscle, which, in the form of a round ligament, passes through 

 a hole in the lower valve, and is firmly cemented by the inter- 

 vention of a calcareous wafer. In a somewhat similar manner 

 the Terrebratulae are fixed by a short ligament ; while the Lin- 

 gula anatina is raised and supported on a cylindrical cartila- 

 ginous peduncle, a few inches long, and capable, apparently, 

 of a certain degree of contraction and elongation. The mus- 

 cles, the Pinnae, some pectens and A'rcae, are moored by what 

 is vulgarly called the beard of the fish, but in the language 

 of science the byssus. This consists of a bundle of blackish 

 horny fibres or threads, connected to the animal within the 

 shell on the one hand, and to the rock on the other. These 

 threads are formed, according to Cuvier and most authors, of 

 a glutinous matter, secreted by a conglomerate gland placed 

 at the base of the foot, and drawn out by the evolutions of 

 this organ to their proper length, and moulded to their shape 

 in a longitudinal groove on its surface. Blainville, however, 

 considers this an erroneous account ; for, according to him, 

 the byssus is a collection of dried muscular fibres. The 

 adductor muscle, he says, of these genera is at first, like those 

 of other Mollusca, contractile and living ; but, being protruded 

 beyond the shell, and attached to the rock, it becomes dried 

 and inirritable to a certain extent, and the fibres by their 

 exsiccation become loose from the thready cable, such as 

 we observe it.* 1 know not which of these explanations to 



* Manuel de Malacologie, p. 1 16. — In Fyfe's Compendium of Comparative 

 Anatom?/, p. 309., the following paragraph occurs : — " Many acephalous 

 Mollusca have a locomotive power, in consequence of a muscular appendix 

 or foot, having on each side a set of fibres like silk. This body they can 

 protrude or retract, so as to fix themselves to solid substances, or drag 

 themselves along the sand. This substance is termed the beard, and is 

 exemplified in the fresh-water muscle, where it is situated under and near 

 the fore part of the shell. By means of the beard, the animal has some- 

 times been observed to move to the distance of some yards in a few hours." 

 Indeed ! For nonsense and error this passage has no parallel ; nor should 

 I have quoted it, had the book not possessed some reputation, and been 

 intended for the " use of students." The author appears to have been 

 totally ignorant of natural history, a study, indeed, which some anato- 

 mists affect to despise ; and hence such blunders. 



