ANNULATA.| LOWER PALAZOZOIC ARTICULATA. 127 
Sub-kingdom ARTICULATA Cw. 
=Annulosa Mac Leay, = Diplonewra Grant, = Homogangliata Owen. 
The most striking external characteristic of the multitudinous forms included in this sub-kingdom, is 
the division of the more or less indurated integument into a succession of transverse ring-like segments. 
All animals with jointed bodies belong to it, but a few members of the group (e.g. the Cirripedia) 
scarcely shew this character, and they have accordingly been separated from what we now know certainly 
to be their true allies, even by such observers as Cuvier and Lamarck. One unvarying characteristic of the 
entire group is, however, to be found in the disposition of the nervous system, which distinguishes 
them completely from the preceding group of so-called radiated animals, and from the next higher group, 
or mollusca. From this consideration it is that Grant and Owen have named the division. One pair 
of principal ganglia (representing the brain of vertebrate animals in function and position) is dorsally 
placed over the cesophagus at the anterior end, supplying nerves to all the higher senses—taste, smell, 
hearing, sight, the antenne, &c.; from these, two cords surround the cesophagus, and form two parallel 
lines along the ventral aspect of the body, and on these are symmetrically placed numerous, nearly equal, 
ganglia, usually one pair for each segment of the body; generally speaking, the lower the type the greater 
the number of segments in the body and of ganglionic centres, while the higher the type (whether we 
speak of adult conformation, or the progress of metamorphosis) the greater becomes the nervous cen- 
tralisation, the ganglia coalescing as it were from behind, as the joints of the body diminish in number; 
as the ganglia decrease in number they increase in size, and the intelligence and physical perfection of 
the creature increase in a corresponding ratio. 
The sub-kingdom Articulata includes the five following classes:—1, Annellida (or Annulata); 2, My- 
riapoda; 3; Insecta; 4, Arachnida; 5, Crustacea. 
Ist Class, ANNULATA. 
The animals of this class have long vermiform bodies, composed of a great number of only moderately 
indurated annular segments, only differing from each other in size, except the first, which contains the jaws, 
and generally eyes, and often antennze for touch, and the last, which is perforated by the anus; each of 
the other rings usually is furnished with setze for locomotion, but never provided with articulated legs; the 
blood is red, not (as some writers suppose) from red globules, as in the Vertebrata, but uniformly tinged. 
They have a mouth at the anterior end, followed by a short cesophagus, leading to a stomach, and often a 
gizzard, from which a straight intestine extends directly to the anus, which is dorsally placed in the last seg- 
ment; numerous czeca (or biliary ducts?) enter the stomach on each side. A tortuous pulsating dorsal vessel 
sends the blood from the tail to the head, where it enters a large ventral vessel, which returns the blood 
again to the dorsal one by numerous anastomosing branches at the posterior end. Over the great ventral 
vessel, and chain of ganglia, is another longitudinal vessel, the ‘“‘supra-ganglionic,” into which the blood 
