386 MABEL BISHOP 



tion planes i^ass tliroiiji;!! Uio innor eye of each head before cutting 

 through tlie outer eye of the same head, since the median eyes 

 he at a higher level. The obliquity of the inner eyes compared 

 with each other is almost negligible (fig. 10). The forebrains 

 are cut more or less obliquely, owing to the variations in the 

 level of the t wo heads. Other slight ol)liquities also occur because 

 of the embryonic flexures, which cause confusion in interpreta- 

 tion unless kept constantly in mind. 



EXPLANATION OF FIGURES 



Figures 1, 2, 4, 5, and 6 are drawings by A. B. Streedain from wax-plate recon- 

 struction models made by the author. Upon the perpendicular at the right of 

 figure 4 is indicated in arable numerals the level of the sections of the embryo 

 represented in figures 8 to 20. These figures were made with an Edinger pro- 

 jection lantern and are arranged in serial order. Figure 3 is a free-hand copy of 

 Wilder's pen-and-ink sketches of the embryo before it was sectioned. Cartilage 

 is represented in solid black, muscles by heavy dashes, and nerves in stipple. 

 A or B, designating the members of the teratological head, and rt (right) or It (left) 

 have been added to abbreviations of structures ivherever it seemed that ambiguity 

 inight otherwise exist. Structures of the median region containing a contribu- 

 tion from both members are referred to as conjoined {co) or median. Magnifi- 

 cation of all figures, except figure 3, X 25. 



ABBREVIATIONS 



A, head A d.fu., dorsal funiculus 

 a, artery Dien., diencephalon 

 Alb.gr., alveololabial groove E., eye 



All.gr., avleololingual grrove E.a.me.co., conjoined (median) exter- 



Apx.lat.r., apex of the lateral recess nal auditory meatuses 



Aq.Syl., aqueduct of Sylvius Epg., epiglottis 



B, head B Esoph., esophagus 



b.vb., body of a vertebra Ex.a.me., external auditory meatus 



C.c.nm., caudal cranial nerve-mass Ex.a.me.co., conjoined (median) ex- 

 Cerb., cerebellum ternal auditory meatuses 



Cer.hem., cerebral hemisphere Ex.nr., external nares 



Cer.ped., cerebral peduncle Ex.pt.m., external pterygoid muscle 



Cg.e.a.m., cartilage of external audi- Fb., forebrain 



tory meatus Fc.l.md., fasciculus longitudinalis me- 

 Cg.e.a.m.co., conjoined (median) car- dialis 



tilages of external auditory meatuses F.olf., fila olfactoria 



Chd.pl., choroid plexus G.g., gasserian ganglion 



Ch.typ., chorda tympani nerve G.g.co., conjoined (median) gasserian 

 C.i.e.co., conjoined (median) capsules ganglion 



of internal ears Gn.g., geniculate ganglion 



Cil.g., ciliary ganglion G.s.p., great superficial petrosal nerve 



CO., conjoined Gu.it., genu internum of the seventh 

 Co.rhmb., conjoined rhombencephala nerve 



Crp.str., corpus striatum Hyp., hypophysis 



