44 The Ohio Joiinial of Science [Vol. XVII, No. 2, 



Explanation of Figures. 



All sections were cut 10 micra thick and all reconstructions 

 and drawings were made from transverse sections. Flat 

 reconstructions at 150 diam., detailed drawings at 520 diam. 

 and outlines at 80 diam. were made with a camera lucida. All 

 figures were reduced to one-third and the magnification after 

 reduction is given after the description of each figure. Figures 

 1 to 6 inclusive are from the same embryo. (Plethedon gl. 

 stage m. 9 mm.) from which the flat reconstruction Fig. 30 

 was made. ■ . ■ ■ ::<,<g r^or ' 



Plate II. - 



Figure 1 is a detailed drawing of the profundus near the level of the middle of 

 the crystalline lens and seven sections posterior to the anterior end of the pro- 

 fundus. (See Fig. 2). Large yolk granules appear as light areas in the mesen- 

 chvme. The j^igmented cytoplasm of the ganglion is shown by darker, solid 

 stippling. Sec. (52 X 175. 



Figure 2 is an outline of the section of which a portion is detailed in Fig. I. X27. 



Figure 3 is an outline of a section at the level of the optic stalks and just 

 posterior to the crystalline lens. Sec. 69. X 27. 



Figure 4 is a detailed drawing of the trigeminal complex at the level of the 

 root. (See Fig. 5). The fibrous root of the Gasserian ganglion is shown (Rt. 

 Gass. G.). A profundus root cannot be distinguished in the figure nor identified 

 in the section from which it was drawn. Sec. 90. X 175. 



Figure 5 is an outline of the section of which a jjortion is detailed in Fig. 4. 

 Sec. 90. X27. 



Figure 6 is an outline of a section through the main portion of the Gasserian 

 ganglion half way between its root and its posterior end. The D. L. VII is shown 

 lateral to the Gasserian ganglion which shows the characteristic forking over the 

 first visceral pouch of the pharynx. (Ph. P. 1). Sec. 95. X27. 



Figures 7 to 15, inclusive, are all from the same embryo (Plethedon gl. Stage 

 G. 7 mm.) from which the flat reconstruction of Fig. 31 was made. 



Figure 7 is a detailed drawing of the profundus ganglion at the level of Fig. 8, 

 six sections posterior to the anterior end. The irregular outline of the ganglion 

 is shown and its position relative to a supra-orbital placode of the lateral line 

 series (PI). The placode appears as a thickening of the ectoderm. The nuclei in 

 the inner laver, containing a mitotic figure, are seen to have a radial arrangement. 

 Sec. 52. X"'l75. 



Figure 8 is an outline of the section of which a portion is detailed in Fig. 7. 

 X 27. 



Figure 9 is an outline of the section of which a portion is detailed in Figure 10. 

 This section is at the level of the open optic stalks and the middle of the crystalline 

 lens. Sec. 68. X27. 



