30 The Ohio Journal of Science [Vol. XVII, No. 2, 



The extreme anterior end of the profundus ganglion lies 

 between the ectoderm and the fore brain dorsal to the anterior 

 end of the optic vesicle. Figure 7, (Prof. G.) shows the 

 character of the ganglion near its anterior end. It is a small, 

 ragged mass of pigmented cytoplasm containing nuclei of 

 moderate size and dark staining properties. Mesially and 

 ventrally it is in contact with mesenchyme and laterally it is 

 separated from the ectoderm by a thin layer of mesenchyme, 

 in which some darkly staining nuclei appear. 



An interesting feature observable in this figure (Fig. 7) is 

 the relation of the profundus ganglion (Prof. G) to the large 

 ectodermal thickening (PI.) lateral to it. This thickening 

 is a placode, w^hich farther posterior shows more noticeably 

 the radial arrangement of cells characteristic of the lateral line 

 organs and is identified as a supra-orbital lateral line placode. 

 This placode is apparently formed by proliferation of cells in 

 both layers of ectoderm. The cells of the outer non-nervous 

 layer have no definite arrangement but those of the inner 

 nervous layer lie with their long axes at right angles to the 

 surface. Cell boundaries may sometimes be clearly made out 

 in the placode. Mitotic figures such as seen in Figure 7 (PI.) 

 are numerous in the placode. Both of these facts are in contrast 

 to the condition in the profundus ganglion. (Prof. G.). 



Posterior to the level of figure 7 the ganglion becomes 

 rounder and more compact and definite. Posterior to the 

 optic stalks it lies slightly farther from the ectoderm. Figure 

 9 (Prof. G) shows a transverse section of the ganglion at the 

 point of evagination of the optic stalks and the middle of the 

 crystalhne lens invagination. (C. L.) 



At this level (Fig. 9) the profundus ganglion lies, as before, 

 (Fig. 7) very near the supra-orbital lateral line placode. The 

 boundaries of the ganglion are clean cut and its limits are 

 readily distinguishable from the surrounding mesenchyme (Fig. 

 10, Prof. G). The nuclei seem to vary a good deal in size. 



From a point posterior to the level shown in figure 9, to its 

 root in the medulla the profundus ganglion appears to move 

 mesially. It retains its compactness, but is smaller in trans- 

 verse section than in preceding sections. Gradually it becomes 

 looser in structure and shows a mesial projection until at the 

 level of Figure 11, the profundus is attached to the ventro- 

 lateral region of the medulla by a small, necklike cellular 



