474 PROF. OWEN ON THE ANATOMY 
resolving into the plexus which supplies the retinæ to the lenses at the lower and fore 
part of the compound eye. 
Gastric Nerves.—Two pairs of nerves arise posterior to the ocular pair. The nerves 
of the first pair (n 3, Pl. XXXIX.) pass forward, give filaments to the cesophagus and 
stomach, and are continued on into the hepatic and ovarian substance at the fore part of 
the carapace. 
First Epimeral Nerve.—The nerves of the second pair (on the outer side of the 
symbol » 4, Pl. XXXIX.) diverge, extend along the fore part of the anterior low and 
simple apodeme (11), subdivide, and are lost in the tissues of that part of the segment 
answering, in position, to the epimerals* of the type segment. The term “epimeral ” 
will, accordingly, be given to this and the succeeding serially homologous nerves. 
Second Epimeral Nerve.—A somewhat larger nerve rises immediately behind the 
foregoing; the pair (Pl. XXXIX. » 5) slightly diverge and ascend, when each second 
epimeral nerve bifurcates. One branch coasts along the anterior apodeme, the other 
inclines toward the interspace between that and the second more prominent apodeme, 
supplies muscular fibres thence arising, and gives off a recurrent filament (» 6), traceable 
along the outer ends of the succeeding apodemes (rr-vi, Pl. XXXIX.) at a little dis- 
tance from them, as far as the seventh epimeral nerve, where this begins to ramify. 
Antennular Nerve.—This nerve (n 11, Pls. XXXVII., XXXVIII.) rises from the 
under part of the basé of the brain (a fig. 1, Pl. XXXVIII.), is rather larger than the 
second epimeral nerve, and supplies the first small forcipated pair of limbs—the homo- 
logue of the first or inner pair of antennz in higher and more differentiated Crustaceans. 
Two filamentary nerves rise from the interval between the antennular and antennal 
nerves at the beginning of the lateral parts of the ring (shown in Pl. XXXVIIT.). 
Antennal Nerve.—This nerve (n 111) is more than twice the size of the antennular 
one; it supplies the second limb (Pl. XXXVIII. 111), which is sexually modified in the 
male Limulus polyphemus. This limb, forcipated like the rest in the female, is the 
homologue of the outer and larger pair of antennze in higher Crustaceans ; and its origin 
is præ- or super-cesophageal in Limulus. 
Third Epimeral Nerve.—From the dorsal aspect of the lateral part of the neural ring 
rises the third *epimeral nerve’ (n 7, Pl. XXXIX.) It runs forward and outward 
above the interspace between the second (ib. 11) and third (111) apodemes, and is resolved 
into a plexus of filaments beyond that interspace, which are lost in the glandular and 
other tissues of that region. | 
Mandibular Nerve.—The third limb-nerve (Pl. XXXVIII. z tv), of the same size as 
the second, comes off behind it, from the lateral part of the ring, 8, and supplies the 
limb homologous with the *mandible' (so called) in higher Crustaceans; which limb is 
marked rv in Plates XXXVII. & XXXVIII., where the nerve is traced through the 
coxal and basial joints. 
Fourth Epimeral Nerve.—From the dorsal aspect of the corresponding part of the 
neural ring is sent off the ‘fourth epimeral nerve’ (» 8, Pl. XXXIX.) having the same 
course and apodemal relations as the second and third of this series. 
* Owen, ‘ Lectures on Invertebrata,’ p. 298. 
