228 bulletin: museum of comparative zoology. 



EXPLANATION OF PLATES. 



All figures are from preparations of chick embryos except when otlierwlse stated. 

 All, with the exception of the photomicrographs and diagrams, were drawn with 

 the aid of the camera lucida. The magnifications follow the descriptions of the 

 figures. 



Abbhbviations. 



cl. ...... , Indifferent cell. 



■cL' Indifferent cell. (See explanation of Fig. 16.) 



cl." Indifferent cell. (See explanation of Fig. 16.) 



'cl. coinit " Accompanying '' cell. 



<cl. comit.' . . . . "Accompanying" cell. 



'cl. comit." . . . . " Accompanying " cell. 



'cl. gn Ganglion cell. 



■cl. gn. cil Ganglion cell of ciliary ganglion. 



cl. med. mig. , . . Migrant medullary cell. 



ec'drm Ectoderm. 



gn. cil Ciliary ganglion. (See explanation of Fig. 17.) 



gn. cl." Erroneously engraved for jm. a7. (Fig. 2). 



gn. Gas Gasserian ganglion. 



gn. mx-md. Gas. . . Maxillo-mandibular portion of Gasserian ganglion. 



gn. t'i Transitory ganglion. 



i/b Infundibulum. 



I Lateral. 



m Median. 



mb. lim. ex External limiting membrane. 



ms'e Midbrain. 



ms'ench Mesenchyme. 



mt'e Hind-brain. 



mu. ob. d Dorsal oblique muscle. 



mu. ob. Ventral oblique muscle. 



mu. rt. a Anterior rectus muscle. 



mu. rt. d Dorsal rectus muscle. 



mu. rt. p Posterior rectus muscle. 



mu. rt. V Ventral rectus muscle. 



mu. rt. V. + a. . . . Ventral and anterior rectus musclea. 



"• abd Abducent nerve. 



n. cil. oc'mot. . . . Oculomotor ciliary nerve. 



n. cil. trig Trigeminal ciliary nerve. 



n. oc'mot Oculomotor nerve. 



