122 CHARLES BROOKOVEll 



ventral olfactory ramus and the placode. The ganglion has 

 increased in size so that it is found in as many as eight sections 6 

 micra thick, but does not exceed perhaps forty or fifty cells in 

 number. They are readily distinguishable in most preparations 

 by their deep staining qualities, as compared with surrounding 

 elements like the mesenchyme from which in some cases the gan- 

 glion appears to be separated by a membrane. In most cases the 

 ganglion is compacted into a spherical mass, but in other cases it 

 is considerably elongated in the same direction with the length 

 of the olfactory ramus, and in one case showed the appearance of 

 two ganglia. As no models of this age were made and the sec- 

 tions are oblique to the nerve, the appearance of two ganglia 

 may be an illusion. The ganglion lies nearer the olfactory plac- 

 ode in the earlier of these stages but comes to occupy a position 

 about midway between the placode and the neural tube in the 

 later stages which are nine days old. This is some days after 

 hatching, when the nose has begun to elongate and the placode — 

 or more properly, the olfactory capsule — lies anterior to the 

 forward end of the neural tube. The opening of the nasal capsule 

 remains single for a considerable time after this stage, which has 

 a total body length of 13.5 mm. 



We have sectioned the two or three specimens available from 

 this series of embryos at the age of 272 hours from fertilization, 

 when they are nearly eleven days old, 48 hours older than the 

 last stage described. The length has almost doubled in the two 

 days and totals 24 nnii., with the sucking disk decadent. No 

 d(3ubt part of this rapid growth in length is due to the growth of 

 the snout, carrying the nasal capsules far in advance of the brain 

 (fig. 12). We have studied a transverse series of this age and it 

 reveals the same distribution of cells of the nervus terminalis as is 

 shown in figure 12, which is a flat reconstruction from a number of 

 sagittal sections. The main ganglionic mass of cells is located 

 in a swelling near the brain, on the ventro-median side of the 

 olfactory nerve. The black dots peripherally along the nerve 

 indicate the position and approximate number of cells outside 

 the ganglion that are to be attributed to the nervus terminalis. 

 As material was not at hand for the application of neurological 



