34 EDGAR J. ALLEN. 
The observations will be dealt with in the following order: 
I. Elements arising from cells situated in the THoracic 
GANGLIA. 
(2) Elements of types the same as or similar to those 
previously described. 
(6) Elements belonging to types not previously described. 
I]. Elements arising from cells situated in the ABDOMINAL 
GANGLIA. 
III. Elements arising from cells outside the central nervous 
system. 
I. Tuoracic GANGLIA. 
(a) ELEMENTS SIMILAR TO THOSE PREVIOUSLY DESCRIBED. 
B, Tuorax xt! (fig. 1).—The cell lies in the anterior 
portion of the lateral mass of ganglion-cells of Thorax x1, 
and gives off a fine fibre, which passes into the neuropile 
( punkt-substance”’), and there breaks up into three main 
branches. Of these branches one passes forwards into the 
next ganglion in front, another backwards to the ganglion 
behind, whilst the third curves round the central ganglion- 
cells, and, keeping close to these, runs forward towards the 
brain on the opposite side of the cord to that on which its 
cell lies. 
By actual observation this fibre has been traced as far for- 
wards as Th. viii, but there can be no doubt that it behaves 
in the same way as B, Th. v, and B, Th. vii (Pt. I, pl. 35, 
fig. 3),? and runs forward to the brain. A comparison of the 
three elements makes it evident that they belong to one and 
the same system, B, Th. vitt, and B, Th. x1, especially resem- 
1 The denomination of the elements to be adopted here will be a continua- 
tion of the system used in the first paper. On comparing fig. 1 of this paper 
with fig. 1 on Pl. 35 of Part I (this Journal, vol. 36), it will be seen that in 
the present case the lateral mass of ganglion-cells in each ganglion (shaded 
blue) is more completely divided into an anterior and a posterior portion by 
the neuropile (left white in the figure) and the fibres of the anterior nerve-root. 
The present diagram represents more nearly the appearance presented by very 
late embryos, whilst the former figure represents that found in earlier ones. 
2 This Journal, vol. 36. 
