EXPLANATION OF PLATES. 915 



EXPLANATION OF PLATES 4653!. 



COMPLETE LIST OF REFERENCE LETTERS. 



A. Anus. a. Dorso-lateral horn of white matter in brain, a.g. Accessory gland 

 of male (modified accessory leg gland), at. Antenna, at. n. Antennary nerve, b. 

 Ventro-lateral horn of white matter of brain. b. c. Body-cavity. bl. Blastopore. 

 C. Cutis. c. Postero-dorsal lobe of white matter of brain. e.g. Supracesophageal 

 ganglia, cl. Claw. c. m. Circular layer of muscles, co. Commissures between the 

 ventral nerve-cords, co. i. Second commissure between the ventral nerve-cords. 

 co 1 . 2. Mass of cells developed on second commissure, cor. Cornea, c. s. d. Com- 

 mon duct for the two salivary glands. . cu. Cuticle, d. Ventral protuberance of 

 brain. d. 1. m. Dorsal longitudinal muscle of pharynx. d. n. Median dorsal nerve 

 to integument from supraoesophageal ganglia, d. o. Muscular bands passing from the 

 ventro-lateral wall of the pharynx at the region of its opening into the buccal cavity. 

 E. Eye. E. Central lobe of white matter of brain, e. n. Nerves passing outwards from 

 the ventral cords, ep. Epidermis, ep.c. Epidermis cells. F. i, F. a, &c. First and 

 second pair of feet, c. f. Small accessory glandular tubes of the male generative 

 apparatus. F.^. Ganglionic enlargement on ventral nerve-cord, from which a pair of 

 nerves to foot pass off. f. gl. Accessory foot-gland. F. n. Nerves to feet. g. co. 

 Commissures between the ventral nerve-cords containing ganglion cells, g. o. Gene- 

 rative orifice. H. Heart, h. Cells in lateral division of body-cavity. hy. Hypo- 

 blast, i.j. Inner jaw. j. Jaw. j. n. Nerves to jaws. L. Lips. /. Lens. /. b. c. 

 Lateral compartment of body-cavity, le. Jaw lever (cuticular prolongation of inner 

 jaw lying in a backwardly projecting diverticulum of the buccal cavity). /. m. Bands 

 of longitudinal muscles. M. Buccal cavity. M 1 . Median backward diverticulum of 

 mouth or common salivary duct which receives the salivary ducts, me. Mesenteron. 

 mes. Mesoblastic somite, m. 1. Muscles of jaw lever, m. s. Sheets of muscle passing 

 round the side walls of pharynx to dorsal body wall. od. Oviduct, ce. OZsophagus. 

 a's. co. OZsophageal commissures, o.f. g. Orifice of duct of foot-gland, o.j. Outer 

 jaw. op. Optic ganglion, op. n. Optic nerve, or.g. Ganglionic enlargements for 

 oral papillae, o r. n. Nerves to oral papillae, or. p. Oral papillas. o. s. Orifice of 

 duct of segmental organ, ov. Ovary, p. Pads on ventral side of foot. p. Common 

 duct into which the vasa deferentia open. p. c. Posterior lobe of brain. /. d. c. 

 Posterior commissure passing dorsal to rectum. /./. Internal opening of nephridium 

 into body cavity, ph. Pharynx, pi. Pigment in outer ends of epidermic cells, pi. r. 

 Retinal pigment, p. n. Nerves to feet. p.p. Primary papilla, pr. Prostate. R. 

 Rectum. Re. Retinal rods. R. m. Muscle of claw. s. Vesicle of nephridium. j 1 . 

 Part of 4th or 5th nephridium which corresponds to vesicle of other nephridia. 



1 The explanations of the figures printed within inverted commas are by Professor 

 Balfour, the rest are by the Editors. 



