BRANGHIAL SENSE ORGANS IN ICHTHYOPSIDA. 155 
vagus ganglion (vg. gl.) above gill-cleft, and just separating from skin. In 
separating, leaving a nerve behind. p. 47. 0. Branchial sensory thickening. ° 
phr. Pharynx. cl. Cleft. T.ocellata. Z. D, oc. 2, cam. luc, 
PLATE X. 
Fie. 37.—Horizontal section through head of a Torpedo embryo. Shows 
hyoid praebranchial nerve (p. 47. 2.) forming in epiblast. 
Fie. 38.—High power view of small piece of preceding section, showing 
hyoid preebranchial nerve (p. d7. 2.) in epiblast. Z. ¥F, oc. 2, cam. 
Fic. 39.—Horizontal section through Torpedo embryo. Vagus ganglion 
separating from the skin. Lateral line (/. 7.) growing backwards and pushing 
indifferent epiblast (¢. ¢.) away. sp. gl. Spinal ganglion. Z. a, oc. 2, 
cam. luc. . 
Fie. 40.—High power view of part of preceding section, showing lateral 
line forming (/. 7.) indifferent epiblast (¢. e.) being pushed away, and lateral 
nerve (/. x.) splitting off from thickening. me. Mesoblast. T. ocellata. 
Camera luc. 
Fie. 41.—Later stage of lateral line. Further back in trunk. High 
power camera lucida. Shows same things as preceding drawing. T. ocellata. 
Fic. 42.—Drawing combined under camera from several horizontal sections 
of an Elasmobranch embryo. Shows various cranial ganglia fused with their 
branchial sense organs. jg. dr. 0. Primitive branchial sense organ. m. dr. 
Mid-brain. c. g/. Ciliary ganglion. G.g/. Gasserian ganglion. f. g/. Facial 
ganglion. az.gi. Auditory ganglion. g/l. gi. Glossopharyngeal ganglion, 
vg. gl. 1. First vagus ganglion. vg.gl.c. Second, third, and fourth vagus 
ganglion. /./. Lateral line. 7. ”. Lateral nerve. aw. Har. . Notochord. 
sp. c. Spinal cord. 
Fie. 43.—Diagrammatic horizontal section through the various branchial 
sense organs and their ganglia. The reader should conclude nothing from 
the cerebral vesicles figured here. There is probably at least one between the 
trigeminal and seventh nerves, and it is not figured here. 
Fie. 44.—Part of a horizontal section of a six weeks’ old salmon. Shows 
the position and segmental arrangement of the branchial sense organs (7. 0.) 
in the trunk. iz. s. Intramuscular septa. . Notochord. me. Mesoblast. 
Fic. 45.—Diagram of lateral view of an Elasmobranch embryo. Shows the 
central nervous system as plate not yet involuted, the posterior roots of the 
cranial nerves (p. 7.), the branchial sense organs, the dorsal eye (0c.), mouth, 
and gill-clefts. Letters as before. 
Fic. 46.—Similar diagram to show the branches of nerves to gill-clefts. 
The aborted branches in dotted lines. Also shows formation and direction 
of various suprabranchial nerves (s. 4. z.). Vagus represented as supplying 
