92 WILLFAM PATTEN. 



EXPLANATION OF PLATES 3 and 4. 

 Reference Letters to Plates 3 and 4. 



a. 2 — 6. Anterior haemal nerves of the second to the sixth neuromere. 

 J. B. Accessory braiu. a. e. Anterior edge of dactylopodite, a, w. Ante- 

 rior wall of the optic ganglion invagination, a. w. c. Anterior wall of cerebral 

 vesicle, b. e. Last point of union of cerebral hemispheres with surface ecto- 

 derm, c. Posterior fore-brain commissure, c". First post-oral commissure. 

 c. h. Cerebral hemispheres, c. K . Uncovered part of cerebral hemispheres. 

 c. m. Canal between the cerebral hemispheres and the thin median ectoderm. 

 c. m. e. t. Canal leading to the median eye-tube. com^. Posterior cerebral 

 commissure, c. r. crura cerebri, c. s. Internal cerebral lobe = corpus 

 striatum, c. si. Invagination cavity of the semicircular lobes, cu. Cuticula. 

 c. V. Cerebral vesicle. D. S. Dorsal surface. F. B. Fore-brain, g. I. ol. n. 

 Ganglion to the lateral olfactory nerve, g. n. 1 — 5. Nerves to gills, g. p. n. 

 Ganglion to pedal nerve = "neural ganglion" of a Vertebrate cranial nerve. 

 g. st. n. Ganglion to stomodeeal nerve. U. B. Hind brain, h. n. 2 — 9. 

 Haemal nerves or peripheral tegumentary nerves, i. Unroofed space corre- 

 sponding to " iter." i. v. Continuation of the invagination of the optic 

 ganglion with that of semicircular lobes. i. v. op. g. Invagination cavity 

 in optic ganglion. i. v. si. Cavity of semicircular lobes. I. e. Lateral 

 eye. I. e. n. Lateral eye-nerve. /. ol. n. Lateral olfactory nerve, l. t. 

 Lamina terminalis. m. 2 — 6. Median haemal nerve of the 2 — 6 neuro- 

 meres. M. B. Mid-brain, m. c. Middle commissure of the brain, m. c. 

 1 — 2. Two cortical masses of ganglion-cells in front of cheliceral nerves. 

 m. cbr. I. Median cerebral lobe. m. c.f. Margin of fold growing over cere- 

 bral hemispheres, md. n. 1 — 5. Mandibular nerve, or nerve to the endo- 

 podite. m. e. Median eye. m. e'. Diverticulum from median eye. m. e. t. 

 Median eye-tube. ni.f. Furrow leading from uncovered portion of cerebral 

 hemispheres to the uncovered portion of the crura, m.f. c. r. Margin of the 

 ectodermic fold growing over the crura, m. ol. n. Median olfactory nerve- 

 m. p. com. Medulla of posterior commissure, m. st. Mittelstrang. mt. n. 

 nerve to chelaria. ne. 1 — 4. Neuromeres. n. p. Anterior neuropore ; leads 

 into brain cavity and into median eye-tube. ol. b. Olfactory buds. ol. I. Ol- 

 factory lobes, ol.o. Olfactory organ, op. g. Optic ganglion, o.g.l — 3. 

 Lobes to optic ganglion, op. 7i'. Nerve to operculum, p. 2 — 6. Posterior 

 haemal nerve of 2 — 6 neuromeres. p. c. Posterior commissure, p. c. s. Ped- 

 uncle to internal cerebral lobe (corpus striatum), p. e. Posterior edge. 

 p. e. c. Medullary nucleus at root of parietal eye-nerve, p. g. Pigment 

 granules, p. n. 1 — 6. Pedal nerves, p. op. g. Peduncle to optic ganglion. 

 p. ol. 0. Primary olfactory organ, p. st. Stalk to the pigmented plexus 

 arising from the primary olfactory organ, r. Bostrum. r. m. e. n. Roots 



