480 . PROF. OWEN ON THE ANATOMY 
longitudinal extent of the hepatic lobes or primary divisions of the gland (as shown at n”, 
fig. 1, Pl. XXXVI.). The gathering tubes of the initial or acinal ducts of these lobes 
course, in the main, transversely toward the intestine until they quit the lobe, when they 
converge abruptly to form the terminal duet. The anterior of these receives the tribu- 
tary ducts of the four chief anterior divisions of the liver; the posterior terminal duct is 
formed by the union of the same number. The ducts of two or three of the anterior 
lobes unite to form that which enters the main or terminal anterior duct; those from 
the four posterior lobes unite and enter the posterior terminal duet by two canals. The 
arrangement, however, shown in the subject of fig. 1, Pl. XXXVI., may be varied in 
other specimens. But the principle of segmental constitution, as here exemplified, will 
be found, I doubt not, in all Limuli. It indicates the liver to have been developed, in 
relation to the primitive composition of the cephaletron, of seven or more antero- 
posteriorly succeeding segments, and that there was a pair of livers or hepatie lobes to 
each. It interestingly exemplifies the way of subsequent concentrative growth charac- 
teristic of the mature and procreative individual. 
The bile is conducted to the intestine by two terminal ducts on each side: the first 
pair (fig. 1, Pl. XXXVI., & fig. 2, Pl. XXXVII., /) open upon the sides of the beginning 
of the tube, where it contracts to the ordinary calibre; the second pair (ib. m) open about 
9 lines beyond, and nearer the dorsal part of the intestine. 
As in the King-crabs, certain Spiders (Zpeira, e. g.) have their ventral mouth + pro- 
vided anteriorly with a chitinous plate, * labrum or * prostome,' and posteriorly with a 
labium or * metastome,' which is soldered to the cephaletral plastron, not bifid and movable 
as in Limulus (Pls. XX XVII. € XXXVIII.*). The cesophagus rises, at first, vertically 
dorsad, then bends back at a right angle, traversing in that part of its course the neural 
ring before expanding into the stomach. This cavity is, in most spiders, produced into 
cæcal appendages, which, in some, extend into the basal joints of the cephalateral limbs. 
The bile-ducts open into that part of the intestine which traverses the thoracetron 
(* abdomen ' of arachnologists). The proportion of difference to resemblance must be kept 
in mind when speculating on the degree of affinity of Xiphosura and Arachnida. 
§ 6. Sanguiferous System.—The dissection of the Limulus was commenced from that 
aspect or plane of the body next to which, in Invertebrates, is the part of the neural 
axis called * supercesophageal,’ and which, as it supplies nerves to the organs of sense, 
answers to the brain in Fishes. As in these Vertebrates, also the removal of the neural 
or dorsal part of the skeleton (Pl. XX XVI. fig. 2) exposes the vascular system (ib. a, a) 
analogous to the so-called ‘aorta’ of Fishes, and homologous with the * dorsal vessel’ in 
Insects. In Zimulus the walls of this vasiform heart exhibit muscular and valvular 
structures, for the same purpose or office as those of the vertebrate * heart.’ 
In a specimen dissected, with a carapace, or upper crust of the two chief parts of the 
body, 9 inches in length, the heart was 4 inches 8 lines in length (Pl. XXXVI. fig. 2, a, a). 
It was included in a delicate membranous sac analogous to a pericardium, but forming, 
in fact, the wall of a venous sinus. This wall consists of two layers. One may be 
properly termed a *tunie:' it includes extremely delicate fibres, chiefly transverse, but 
T a, fig. 109, * Lectures on Invertebrata,’ 8vo, 1843. 
