860 RECORD OF CURRENT RESEARCHES RELATING TO 



matter secreted by the muscles, while Poll looked upon the muscular 

 " languct " as being quite secondary. Blainville and others have 

 regarded the byssus threads as being dried muscular fibres, and Leydig 

 as being formed of chitiuized fibres. The first correct account is 

 due to A. Miiller, who described the acinous glandula hyssijjara in 

 the groove of the foot of Mytilus ; Siebold (1848) agreed in the 

 main with A. Miiller, and suggested that the byssus threads were 

 formed at the base of the byssal pit by lamellfe in very much the 

 same fashion as the human nail is developed on the fingers. In 

 1877, Tycho Tnllberg returned to the subject, and investigated 

 the characters of the byssus in Mytilis edulis ; he observed the 

 presence of two glandular masses, one whitish and one greenish in 

 colour ; he found that the latter was j)laced towards the tip of the 

 foot and opened by ramified tubes into the semilunar cleft, while the 

 whitish gland was placed on either side of the groove and poured its 

 secretion directly into it. 



M. Carriere finds that in the anterior portion of the tongue-shaped 

 and comparatively freely movable foot there is a large hyssus-gland, 

 which opens into a gland more or less semilunar in shape; this 

 groove is directly connected with the cleft which extends along the 

 margin of the foot, but it may, by the closure of its walls, form a 

 somewhat semilunar canal. Behind the gland there is placed the 

 " second characteristic organ," the byssus-cavity, which is occupied 

 by fan-shaped processes, between which are placed the byssal lamellae, 

 which form the byssus proper. 



As to the epithelium which covers these processes, it is to be 

 noted that there is no ciliated epithelium, but only cylindi'ieal cells, 

 in those in which — e.g. Mytilus, Dreissena— the byssus is best 

 developed ; in those in which — e. g. Pecten, Lithodomus — the byssus 

 has a less complete function of attachment, the processes are some- 

 what atrojihied, and the non-functional regions are covered with 

 ciliated epithelium ; while in others — e. g. Lima — in which the byssus 

 merely forms, with other substances, a kind of bed, the whole of 

 the byssus-cavity is invested with ciliated epithelium. 



It is, of course, impossible to follow the author through his 

 extended observations on some twenty-five species; those of our 

 readers who want his results in short will find on pp. 80-82 a list 

 of the Siphoniate and Asiphoniate Lamellibranchs as to which 

 M. Carriere is able to give any information. The author is of opinion 

 that the byssus-lamellaj are secreted by the byssus " fans " or rather 

 by the epithelium of these processes ; while as to a more general 

 result we may add this : the byssus-gland was primitively possessed 

 by all the Lamellibranchiata, some of which have, in the course of 

 time, lost it as a functional organ, but its presence is constantly 

 indicated by the possession of rudimentary byssus-organs in the 

 shape of glands, sacs, or clefts. The author also thinks that the 

 orifices and clefts found in the foot only serve for the exit of 

 the glandular secretions, and that they have no communications 

 with the vessels or with the lacunro of the body (in consequence 

 of their unbroken investment of epithelium) ; if this view be cor- 



