44, EDGAR J. ALLEN. 
and satisfactory. The same elements are seen again and again 
with such frequency, that little doubt can remain as to the 
accuracy of an observation. 
The elements of the abdomen are similar in kind to those 
described for the thorax, and will be considered under the 
same general headings. 
ELEMENTS OF WHICH BOTH CELL AND FIBRE LIE ENTIRELY IN 
THE Gane ionic Cua1n.—In each of the abdominal ganglia, 
from Abd. 11 to Abd. v1, a pair of elements similar to that 
represented in fig. 6, B (2) has been found to exist. Each 
element has its origin in a large cell situated in the anterior 
lateral portion of the ganglion near its ventral surface. From 
this cell a fibre arises which runs inwards and backwards, de- 
cussating with its fellow of the opposite side at the middle line 
and subsequently giving rise to two fibres, one of which runs 
backwards, whilst the other runs forwards towards the brain. 
The backward branch breaks up into fine fibres in the neuro- 
pile of the ganglion in which the cell lies. The forward branch 
runs as a longitudinal fibre along the ganglionic cord and in 
all probability enters the brain. Unfortunately, owing to 
difficulties of technique, it has never been possible to trace a 
single longitudinal fibre of one of these elements through its 
entire course, but a consideration of the whole evidence leaves 
little doubt as to their entrance into the brain. One of the 
most satisfactory direct observations was made upon an embryo 
near the point of hatching, in which the abdominal ganglia 
had been dissected out, as described above. In such prepara- 
tions the pair of elements under consideration most frequently 
stains in Ab. 11, and the fibres can generally be traced forwards 
through Th. x and 1x. In one preparation, however, where 
there was a wound at the level of Th. 111, the fibres of the 
elements upon both sides were distinctly visible as far forwards 
as this point. 
But it is in embryos at an earlier stage, in which the 
abdomen has been left uninjured, that these elements most 
frequently appear. In order to make the evidence clear it is 
