510 PROFESSOR E. RAY LANKESTER, 
tiniform organs,” considers that eight pairs of ganglia are 
thus represented, a pair for each of the walking legs, a pair 
for the chilaria, and a pair for the genital operculum. The 
4 chilaria appear to me (as explained below) to be simply 
sternites,” and not related to the Scorpion’s “combs;” and 
and I should therefore consider only seven pairs of segmen- 
tal ganglia to be represented in the cesophageal collar. The 
_ history of development is not yet quite definitely ascertained, 
but it should decide this point, and should show, supposing 
the views which I am about to advocate are correct, that 
there is no ganglionic enlargement of the cord corresponding 
to the “chilaria,” whilst the ganglonic enlargement from 
which the genital operculum is innervated should at first be 
more distinctly abdominal in position, and at a later period 
become fused with the six ganglion-pairs corresponding to 
the pediform appendages, 
The third portion of the central nervous system of 
Limulus distinguished as the ABDOMINAL CORD, stretches 
from the cesophageal collar into the abdominal region, and 
gives off no nerves over a space equalling half its total 
length; it then enlarges and gives origin to a series of five 
groups of nerves, of which the first four correspond to and 
supply the four first pairs of branchial feet, whilst the fifth 
supplies not only the fifth pair of branchial feet, but also the 
preanal and perianal regions and the postanal spine. As 
to the disposition of nerve-cells in this ahdominal cord we 
have no information, that is to say, as to whether it is 
possible anatomically to define separate ganglia in connec- 
tion with the five groups of nerves in its hinder part, or in 
any region in front of them. 
A very important relation between the arteries of Limulus 
and the main nerve trunks was first indicated by Owen (18), 
but more fully elucidated by Alphonse Milne-Edwards. This 
consists in the ensheathing of the cesophageal collar and of 
the abdominal cord in an actual arterial trunk; not only 
this but many of the larger nerves (those to the limbs) are 
‘ ensheathed also by branches of the same arterial trunk. 
M. Milne-Edwards has pointed out that this arrangement is 
most nearly approached in Scorpio, and has recognised the 
remarkable agreements between the agterial system of the 
two animals—to which reference will be made further on— 
though he nevertheless is led by other considerations which 
are, I think, erroneous, to refuse to Limulus a position 
among the Arachnida. ; 
When we compare the nervous system of Scorpio, as far 
as it has been made known by Newport and Metschnikoff, 
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