276 
tory cups have been left in position. A pair of cranial nerves is thus 
brought to view that have not been heretofore described. Each nerve (xv) 
arises from the summit of the fore-brain, near the median plane, and 
passes laterally into communication with the main olfactory and thence 
into the olfactory cup. The median attachment to the brain-wall is 
near the closed neuropore, and at this stage bears a small ganglionic 
enlargement (gl). The lateral bundles of olfactory fibres (a and 6) 
have also an independent connection with the brain-wall. This con- 
nection is of a complex nature and consists in reality of two roots. 
We have, therefore, existing simultaneously two separate and distinct 
connections between the ol- 
factory epithelium and the 
brain- wall — a median dorsal 
and a lateral — and the latter 
has two roots. 
The median nerve (nv) 
existe in much earlier stages 
than that represented in Fig. 1, 
and, according to my obser- 
vations it is the first one to 
be found. It has at first a 
connection (placode) with the 
thickened surface epithelium 
Fig. 1. > about 25 diameters explanation lying just above the shallow 
in the text. depression that marks the be- 
ginning of the olfactory pit. I 
have given much attention to the sections of embryos 6 to 8 mm long, and 
there exists in these young stages a cellular connection between the olfac- 
tory plate and the brain-wall as described by Horrmann !). In embryos 
about 10 mm long it can be determined that there is a fibrous connection 
between brain-wall and olfactory epithelium. The precise stage at 
which the attachment shows fibres is not of so much importance as 
the fact that there is in the earliest stages only a single connection 
between brain-wall and nasal membrane. Presently, a second indepen- 
dent attachment to the brain-wall arises. This second connection is 
present in embryos 13 mm long, and by the time the embryo has 
reached 16 mm in length, it is clearly differentiated. From this latter 
stage, onwards, I have traced these two independent sets of nerve 
fibres into the sub-adult stages. The two brain connections are at 
1) Morph. Jahrb., Bd. 24, 1896, Heft 2, p. 270. 
