550 MYRIAPODA. 
fat Nags on ype it on ‘all sides, are seen 
to rated at intervals . 
with papa valvular ori- Fig. 312. 
fices, through which the cir- 
culating fluid gains free admis- 
sion from the general cavity 
of the body, and by the un- 
dulatory contractions of the 
dorsal heart thus constructed 
is forced forward toward the 
head. Arrived in the neigh- 
bourhood: of the csophagus, 
the dorsal heart is seen to give 
off several vessels, and ac- 
cording to the opinion of Mr. 
Newportand Mr. Lord,* there 
is reason to suppose that a 
vascular system more com- 
plete than has as yet been 
proved to exist in any of the 
true Insects may be pointed 
out in this region of the body. 
The dorsal vessel itself, when 
examined under a microscope, 
is distinctly muscular, being 
formed of circular flat bands 
that surround the cavity of the 
tube, so that doubtless the 
action of this heart, in the 
larger species at least, is suffi- 
ciently energetic. 
Foramina repugnatoria.—These are a series 
of orifices which in the Julide are seen upon 
the lateral aspect of every segment of the body, 
and communicate with as many minute mem- 
branous sacculi placed within the body. These 
sacculi, both from their position and relations, 
forcibly remind us of the series of respiratory 
sacs met with in the Leech and other air- 
breathing Annelidans, but in Julus they are 
supposed to be merely organs of secretion from 
which some offensive fluid is poured for the 
protection of the animal. 
Nervous system.—The nervous system of the 
Myriapoda, as in all the Articulata, exhibits a 
double series of ganglia connected by cords of 
inter-communication. The supra-cesophageal 
ganglion, situated within the cephalic segment 
of the body as relates to its development, 
seems to hold a place intermediate between 
that of the Annelida and of Insects, or perhaps 
more strictly speaking, corresponds with the 
larva condition of the latter. The ventral chain 
of ganglia is numerous in proportion to the 
nutaber of segments which enter into the com- 
position of the body, their number decreasing 
as the locomotive limbs over which they preside 
become more fully nererepes and capable of 
more vigorous action. hus in Julus and 
Geophilus, where the limbs are extremely 
numerous and feeble, the ganglia in their num- 
ber and small size a ener the condition 
they exhibit in the Nereis or more elevated 
Annelides, but in Scolopendra (fig. 313) the 
more powerful limbs and stronger muscles 
required by their carnivorous habits demand 
greater developement of the centres of the ner- 
vous system. 
* Vide Med. Gazette for 1837. 
“il 
Senses.—In the structure of their or 
sensation likewise, the Myriapoda so 1 
