GENERAL DESCRIPTION AND RELATIONS.--Slender and elongate; on posterior surface of tarsometatarsus medial to midline; belly (except proximal end) adjacent (lateral) to posterior metatarsal crest; proximal end passing under latter (immediately distal to hypotarsus) and lying anteromedial to hypotarsus. ORIGIN.--The origin is fleshy from the medial metatarsal depression and from the posterior surface of the tarsometatarsus between the midline and the posterior metatarsal crest beginning immediately below the hypotarsus and ending a short distance above the first metatarsal (sometimes more proximally). INSERTION.--The slender tendon, which begins along the medial edge of the distal part of the belly, passes through the groove on the posterodistal surface of the first metatarsal and onto the proximal end of the ventral surface of the hallux; the tendon widens considerably and attaches by its edges to the ventral surface of the proximal end of the first phalanx, forming a short "tunnel" through which the tendon of M. flexor hallucis longus passes. INNERVATION.--The paraperoneal branch of the tibial nerve sends one or two twigs into the proximal part of the muscle (but distal to the hypotarsus). INDIVIDUAL VARIATION.--In two legs, the muscle arises in part from the distal end of the lateral calcaneal ridge. The individual variation is insignificant in _T. cupido_ and _P. p. jamesi_. DISCUSSION AND CONCLUSIONS _Analysis of Individual Variation_ Considerable individual variation occurs in both the muscles and the nerves of the leg of the three species studied. The amount of variation reported by a worker depends in large part on the degree of variation that he considers significant. Individual variation in the muscles and in the nerves will be discussed separately; that of the muscles (excluding innervation) will be considered first. Muscles Considering the number, rather than degree, of variations, the most variable muscles are: Mm. flexor digitorum longus, obturator, caudofemoralis, and extensor hallucis longus. The first-mentioned muscle exhibits 14 different variations in the specimens studied. Mm. vastus lateralis, flexor perforans et perforatus digiti II, and piriformis also showed a considerable number of variations. The following muscles did not exhibit any variations considered significant in this study: Mm. vastus medialis, femoritibialis internus, flexor perforatus digiti III, extensor brevis digiti III, and abductor digiti IV.