NERVE ENDORGANS IN THE EAR 293 
To this much mooted and interesting question, then, I wish to 
contribute the modest results which I have been able to obtain 
from my study of Trigonocephalus japonicus. 
The viperid embryos which were placed at my disposal comprise 
more than 27 stages! (Suzuki-Okajimas series), of which I have 
employed four for the present study. The embryos were fixed 
in formol-alcohol, potassium bichromate-acetic and corrosive 
sublimate-acetic and were stored in alcohol until stained and im- 
bedded in paraffin. Mainly frontal sections 10-15u thick were 
made through the heads of the embryos. These were stained 
in toto with alcoholic borax carmine and Weigert’s iron haema- 
toxylin, and in the latter case orange G was employed as a counter 
stain. The two adult specimens were fixed in potassium bi- 
chromate, imbedded in celoidin and cut vertically through the 
head. These sections, 30u thick, were stained in haematoxylin- 
eosin and orange G. 
Stage 1 (fig. 1). The embryo is coiled up in 4% turns. Ol- 
factory pit very deep. Wall of optic cup thickened anteriorly; 
lens solid. Fixation: corrosive-acetic. Stain: Weigert’s iron 
haematoxylin; sections 15u. Frontal sections of head and body. 
The auditory vesicle, which is distended into a sac-like struc- 
ture, is already oval in shape and, since it runs through 47 sec- 
tions, is about 0.705 mm. in antero-posterior diameter. It lies 
some distance removed from the brain. Differentiation in the 
epithelial lining of the wall of the auditory vesicle is already 
apparent. Laterally the epithelium is flattened, while the medial 
and lower walls are stratified several cells deep and show here and 
there a mitotic figure. This thickened portion represents the 
common neuroepithelium which will later separate into the pars 
superior and the pars inferior. The ductus endolymphaticus is 
already tubular in form, with the dilated saccus endolymphaticus 
at the end. 
Stage 2 (fig. 2) The embryo consists of 314 coils. The 
parietal elevation is prominent. The lens is approximately as in 
the preceding stage; the retina moderately pigmented. The 
1 The number includes 7 sectioned by the writer. 
