16 



First Epimeral Nerve. — The nerves of the second pair (on the outer side of the 

 symbol n 4, PI. V.) diverge, extend along the fore part of the anterior low and simple 

 apodeme (ii), 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 ' wiU, accord- 

 ingly, be given to this and the succeeding serially homologous nerves. 



Second Epimeral Nerve. — A somewhat larger nerve rises immediately behind the 

 foregoing; the pair (PI. V. n 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 reciu'rent filament {n 6), traceable along 

 the outer ends of the succeeding apodemes (ii-vi, PL V.), at a Httle distance from them, 

 as far as the seventh epimeral nerve, where this begins to ramify. 



Antennular Nerve. — This nerve {n ii. Pis. II., II a.. III., IV.) rises from the under 

 part of the base of the brain (a fig. 1, PI. IV.), is rather larger than the second epimeral 

 nerve, and supplies the first small forcipated pair of limbs — the homologue of the first or 

 inner pan* of antennae 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 PI. IV.). 



Antennal Nerve. — This nerve {n iii) is more than twice the size of the antennular 

 one ; it supplies the second limb (PI. IV. iii), which is sexually modified in the male 

 Limulus pohjphenius. This limb, forcipated like the rest in the female, is the homo- 

 logue of the outer and larger pair of antennae in higher Crustaceans ; and its origin is 

 prse- or super-oesophageal in Limulus. 



Third Epimeral Nerve. — Prom the dorsal aspect of the lateral part of the neural ring 

 rises the third ' epimeral nerve ' {n 7, PI. V.). It runs forward and outward above 

 the interspace between the second (ib. ii) and third (iii) 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 (PI. IV. n iv), of the same size as the 

 second, comes off behind it, from the lateral part of the ring, /3, and supplies the limb 

 homologous with the ' mandible' (so called) in higher Crustaceans ; which limb is marked 

 IV in Plates II. & III., 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, PI. V.) having the same course 

 and apodemal relations as the second and third of this series. 



Premaxillary Nerve. — This, with a more posterior origin than the mandibular nerve, 

 repeats the characters of that nerve, in relation to the fourth limb, or homologue of the 

 ' prsemaxilla,' or first or anterior maxilla, in higher Crustaceans. The nerve {n v) is 

 shown in Plates II. & III., entering and traversing the 'coxa' and 'basis' of the limb 

 marked V. This limb is sexually modified in the male of Limulus moluccanus, but not 

 in the species here dissected. 



Fifth Epimeral Nerve {n 9, PI. V.). — This repeats the relative position of origin to 



• Owen, ' Lectures on Invertebrata,' p. 298. 



