274 
MR. NEWPORT ON THE NERVOUS AND CIRCULATORY SYSTEMS 
vessels in Myriapoda and in insects. The bifurcation and distribution of the aortal 
portion of the dorsal vessel in insects was noticed in the first paper which I had the 
honour of submitting to the Royal Society *, and was also figured in a subsequent 
one-f-, in which I described a structure that had previously been seen by Treviranus 
in the Scorpion, who believed it to be part of the nervous system, and by Muller, 
who thought it was a ligament. This was also described by myself as a nervous 
structure, although subsequent examinations led me to suspect it was vascular, a 
suspicion which afterwards was found to be correct, by the discovery by Mr. Lord;*; 
that this structure in the Scolopendra has a direct communication with the anterior 
part of the dorsal vessel, by means of two lateral vascular arches, the continuations 
of the two lateral divisions of the dorsal vessel observed by Straus in the head of Sco- 
lopendra. These arches, descending one on each side of the oesophagus, and meeting 
in the middle line beneath it, form this single median vascular trunk, which is ex- 
tended backwards above the abdominal nervous cord. The facts ascertained by 
Mr. Lord were immediately confirmed by my own observations, and the correspond- 
ing structure in the Scorpion was also shown to belong to the vascular system §, and 
to form in like manner a vascular collar around the anterior part of the alimentary 
canal. In addition to this vessel lying above the nervous cord, I then first described 
another system of vessels extended beneath it, the chief of which, placed immediately 
beneath the cord, communicates with the upper vessel, both anterior and posterior 
to each ganglion, by means of very short branches, while the inferior one is also con- 
nected with a system of vessels that ramify in the inferior part of the abdominal seg- 
ments. I also noticed the existence of a large vascular trunk that is extended along 
the abdominal cord in perfect Lepidopterous insects, so that distinct vascular trunks 
were thus shown to exist in Myriapoda, Arachnida, and Insecta, similar to those 
already known in the Crustacea. Since that period I have succeeded in tracing other 
vessels in these classes, the distribution of which, and their connexion with the ner- 
vous system, I will now attempt to describe. 
Structure . — The most rudimentary condition of the circulatory system in Myria- 
poda exists in the Iulidse, the family most nearly connected by its mode of growth, 
as well as by the whole of its structure, with the Annelida. In the lowest genera of 
this family, the Spirostrepti and Spiroboli , Brandt, the structure of the heart is ex- 
ceedingly delicate, and its separate chambers are very numerous. Their number is 
almost equal to that of the segments of the body, being only two less than that of 
the whole number of segments, there being none in the head, or in the anal segment. 
The number of segments varies considerably in the different species, being in some 
of the Spirostrepti not more than forty-four, but in others so many as seventy-two, 
and in Spirobolus even seventy-five, so that in the latter there are sometimes as 
many as seventy-two or three distinct chambers to the heart. This structure is ex- 
* Philosophical Transactions, 1832, Part II. p. 385. f Op. cit. Part II. 1834. Plate XIV. fig. 12 k. 
{ Medical Gazette, March 3, 1838, p. 893. § Op. cit. March 17, 1838, p. 971. 
