THE DEVELOPMENT OP LEPIDOSIBEN PAHADOXA. 455 



rigures of a selected luiniber of stages were copied in Tait 11 (this 

 specimen Journal, op. cit.). 



I liave again to express my great indebtedness to Mr. Edwin Wilson for llio 

 care which he lias devoted to working up the figures. 



General List op Reference Letters. 



a.d. Archinephric duct. aud. Auditory vesicle or capsule, a.v. Annular 

 vacuole, b. Bony trabecula. h.c. Buccal cavity, b.v. Blood-vessel. buc. 

 Solid yolk-laden cells occupying position of buccal cavity, r,. Clironiato])liore 

 of Type A. c.^. Cliromatophore of Type B. c.h. Cerebral hemisphere, d. 

 Dentine, d.g. Dorsal root ganglion, e. Enamel, e} Superficial layer of 

 ectoderm, e-. Deep layer of ectoderm, e.o. Enamel organ, e/;. Pineal body. 

 f. Eat globule, f.l. Eore-limb. rj.c. Unicellular glands, g.l. Elask-shaped 

 gland, hyp. Hypophysis cerebri. /.?'. liobus inferioris. m.e. Mesenchyme 

 cells, mes. Mesencephalon, m.l. Membrana limitans. m.n.r. Motor neive- 

 trunk. my. Myotome. n. Notochord. n.a. Neural arch. n.c. Neural 

 tube. nu. Nucleus, o. Odontoblast, ox. Eye rudiment, o.g. Oil globule. 

 olf. Olfactory capsule, j). Bucket. /;//. Phagocyte, r. Bod. scl. Sclerotome. 

 stom. Lining epithelium of buccal cavity arising in situ. ih. Thalamon- 

 cephalon. v. IV. Fourth ventricle. 



The cranial nerves are indicated by the ordinary lloman numerals. In 

 addition: — h.m. Hyomandibular branch, led. Lateral branch. Jat.gang. 

 Lateral ganglion, r.c. Communicating branch, s.p. Superior palatine branch. 

 vise, ffctiig. Visceral ganglion. 



PLATE 25. 



Fig. 1. — Example of tailed cells from the ectoderm of a young Lepido- 

 siren of Stage 35 - . Zeiss 3 mm. apochrom., oc. 2. 



Fig. 2. — Section of skin from the head of an adult Lcpidosiren to show 

 the large unicellular glands {g.c). Zeiss A, oc. 2. 



Fig. 3. — Illustrating the history of the cement organ. Zeiss A, oc. 2. 



A. Stage 23, showing simple thickening of the deep layer of the ecto- 



derm. 



B. Stage 25, showing the disappearance of the superficial layer over 



the gland rudiment. 



