579 
of Edinburgh, Session 1881 - 82 . 
l’on trouve melanges aux gros corpuscles du milieu du ganglion. La 
grandeur de ces corpuscles est uniforme. Ils semblent etre des noyaux 
qui ne depassent pas de faibles proportions. Aussi ne trouve-t-on 
jamais mel^s a eux ces grands corpuscles ganglionnaires qui occupent 
le milieu du cerveau Arrondi du cot6 de la commissure, ce 
lobule semble separe par deux lignes formant un angle du cote du 
ganglion en dehors, on croirait que le n6vrileme l’entoure et Fisole.” 
The author goes on to say that this mass is found in all the 
Pulmonata, and that researches are wanted to establish its functions 
and relations with other parts of the ganglion. It is therefore 
evidently something distinct from the rest of the ganglion. The 
absence of the red pigment, which is so characteristic of the nervous 
system of Lymnseus, is so very remarkable, if this lobe is to be 
regarded as merely a part of the cerebral ganglion ; and again the 
fact that it is divided off from the rest by a connective tissue 
lamella, while none of the other lobes into which the cerebral 
ganglia are portioned show any signs of such a complete separation, 
seem to point to its being a distinct structure. 
Fig. 4 represents a vertical section taken through the cerebral 
ganglion of one side ; b is the commencement of the commissure 
which unites it to the other cerebral ganglion ; e is the commis- 
sure uniting it with the pedal ganglion ; a is the “ white lobe ” 
of the ganglion. A glance at this drawing will show at once how 
different it is in general appearance from the rest of the cerebral 
ganglion; it is made up of small rounded cells packed closely 
together, so as to give the appearance occasionally of being poly- 
gonal. When separated by maceration in weak chromic acid and 
subsequent teasing, each of these cells is oval or roundish, occasion- 
ally three-cornered with the corners rounded off; the nucleus is 
large, but not nearly so large in proportion as the nucleus of the 
ordinary nerve cells from the ganglia ; they are very similar in 
general appearance to certain glandular cells from the penis of the 
same animal, but a good deal smaller, hfo signs of any nerve 
fibres either within the mass or connecting the two were visible. 
In sections of the nervous system prepared with different reagents 
the appearances presented by the “ white lobe ” are very different 
from the rest of the ganglion. When stained with gold chloride, 
the ordinary nerve cells are coloured with various shades of blue 
and purple, the nuclei being left altogether unstained, while the 
VOL. xi. 4 A 
