212 BULLETIN OF THE BUREAU OF FISHERIES. 
also forms a groove lined by strongly ciliated cells with many mucous gland cells 
among them, and this, with the groove of the gill, forms a very long tube which 
conveys food to the mouth. 
Minute structure of the gills.—I\t has been seen that, by their mode of formation, 
the ‘intrafilamentar union” between the two limbs of a lamina is so complete that 
blood may flow freely through the wide, flat blood space of the lamina from the 
afferent to the efferent branchial vein. The ‘‘interfilamentar’” or, better, inter- 
laminar connection between adjacent laminie, is also very extensive, but serves only 
for support and does not permit the full interchange of blood. The general plan of 
the interlaminar connections is shown in figure 39, which is a tangential section of 
a gill almost in the line of the letters 7/7 in figure 38. It is seen that the points of 
union in adjacent laming are arranged in regular rows. At each point the support- 
ing rod (s r, fig. 40) projects through a perforation, so as to bind together adjacent 
laminw, Attached to adjacent rods are fiber-like cells, which are apparently muscular 
and contractile. 
The minute structure of the edge of a lamina is similar to that of the filaments 
in forms like Mytilus, though the various types of cells are more sharply marked off 
from each other. At each side there are two rows of large ‘‘lateral cells” (Lc, fig. 
40), bearing long, dense cilia, External to these are small nonciliated gland cells, 
and at the angles the small, flattened “latero-frontal” cells (Ufc, fig. 40), each with 
a single row of stiff cilia. The outer edge of the laminz is occupied by numerous 
small ‘frontal cells” (fe) which bear numerous weaker cilia. The two broad sides 
of the lamina are composed of very flat cells without cell outlines or regular arrange- 
ment, and are connected together by numerous connective-tissue cells which pene- 
trate the blood space of the lamina (bs, fig. 38, 40). In their minute structure 
(fig. 41) the anterior eleven filaments which are separated from the rest of the gill 
are essentially like the rest of the gill, except that the ‘frontal cells” are more 
numerous, and the middle ones seem to bear no cilia. The first and eleventh fila- 
ments are only half filaments, indicating that the filaments are formed by perfora- 
tions in a gill membrane which is primitive, and not that the membrane is formed 
by the precocious fusion of gill filaments. The long epibranchial canal is sparsely 
ciliated, and it seems that the special function of the anterior eleven filaments is to 
get rid of superfluous water in the anterior end of the burrow. 
Glands of Deshayes.—Closely associated with the gills of the adult is a pair of 
very complicated structures which, so far as known, are peculiar to ship-worms, 
and which constitute one of the most important features which distinguish the ship- 
worms from other types of lamellibranchs. In honor of the observer who first called 
attention to them, I have called them the ‘‘glands of Deshayes.” Though he 
pointed them out they have never been fully described as to character, structure, 
and relations. 
Deshayes observed a peculiar structure in the umbonal region on each side of 
the shell cavity. He described it as of glandular nature and supposed its function 
to be the secretion of a fluid to soften wood in the formation of the burrow. In 
the gill laminwe he described peculiar modifications of the tissues, which he sup- 
posed to be mucous glands and to serve for the nutrition of the viviparous embryos 
of ship-worms. He also described a third structure es invading a part of the walls of 
