392 
processes are unquestionably in connection with the fibres of the ol- 
factory nerve, as many places in my preparations show. Fresh mate- 
rial will be required to elucidate the course of the superficial processes 
of these cells: it is possible that they may only indirectly reach the 
surface through the medium of those more superficial cells with longer 
nuclei which are undoubtedly ,olfactory‘, in which case the deeper 
cells would have to be interpreted as ganglion-cells formed in the course 
of the olfactory fibres to the true olfactory cells 5. However this may _ 
be settled, I think there is no doubt of the identity in structure of the 
deeper parts of the nuclear stratum in the nasal olfactory epithelium 
and the cellular columns of the Organ of Jacobson. 
The following arguments appear to favour the above conclusion: 
1) Reichel? has already called attention to the late development 
of all glandular structures in the head of the Ophidia. in the embryo 
examined neither Müller’s lateral nasal gland, nor Bowman’s glands, 
nor the palatine crypts are developed; the superior labial gland is just 
beginning to be formed while the outgrowths of the neuro-epithelium 
of Jacobson’s Organ are already formed at a much earlier stage. 
(Wanlnomen, gle ea): 
2) Klein has pointed out that the great thickness of the neuro- 
epithelium on the median wall of Jacobson’s Organ in the Rabbit and 
Guinea-pig is due to the increased number of layers of ‚sensory‘ cells 
which may even extend outin small groups into the mucosa. 
Both in this respect and in the fact that the olfactory nerve is entirely 
distributed to it, the median wall of Jacobson’s Organ in the Mamma- 
lia corresponds to its roof in the Reptilia. 
3) In anterior and posterior frontal sections through Jacobson’s 
Organ, where the cellular columns are cut across, I have failed to find 
any indication of a lumen, and indeed the protoplasm surrounding the 
cells is so scanty that it would be impossible to ascribe a secretory 
function to the cells at either of the stages examined. That they pos- 
sess such merely at an earlier stage is abundantly disproved by the 
fact that the columns only attain their full size in the adult. 
6 Wiedersheim (Lehrbuch der vergl. Anat. p. 355) copies a diagram from 
Merkel according to which all the fibres of the higher sense-nerves pass through 
a ganglion-cell before entering their proper terminal cells. Perhaps this is not in- 
tended to include the olfactory nerve-endings, for I do not remember to have seen 
other than a direct communication between olfactory nerve fibres and olfactory 
cells suggested. I cannot refer to Merkel’s work at present. 
7 Morphol. Jahrb. 8. Bd. 1. Hft. 
8 I have considered the possibility of the cellular columns being glands of the 
sort figured by Hoffmann from the olfactory epithelium of Sphargis and Chelone 
(1. ec. T. XXXIV, Fig. 8) the cavities of which are filled by a cellular mass. These 
