ANATOMY 27.3 
The carapace is represented as transparent. The appendages have been removed, 
but the outlines of the left entocoxites (6) have been sketched in. The positions 
of the abdominal appendages are indicated by the external branchial muscles (17), 
the branchial cartilages (19), the tendinous stigmata (18), and the abdominal endo- 
chondrites (21). In the cephalothorax (1) all the tergo-coxal and plastro-coxal 
muscles have been dissected away, leaving the endosternite (11) with the occipital ring 
exposed, One of the left tergo-proplastral muscles (4) and the left branchio-thoracic 
muscles (16) are represented. The longitudinal abdominal muscles are also seen. 
All the muscles of the right side have been omitted except the haemo-neural muscles 
(23), of which the last two are represented upon the left side also. At the base 
of the telson the flexors (29) and extensors (27) of the caudal spine are represented 
as cut off near their insertions. The sphincter ani (26), levator ani, and occludor 
ani (25), and their relations to the anus (28), are shown. 
The oesophagus runs forward to the proventriculus (3), From this the intestine 
(20) passes posteriorly. 
The brain lies upon the neural side of the endosternite, and the ventral cord (22) 
passes back through the occipital ring. The neural nerves are cut off, but the 
left haemal nerves and those from the fore-brain (12) are represented entire. 
The first pair of neural nerves go to the chelicerae. The second to sixth pairs go 
to the next five cephalothoracic appendages, which are represented by the ento- 
coxites (6). The seventh pair of neural nerves go to the chilaria, and the eighth 
pair to the operculum. The neural nerves from the ninth to the thirteenth arise 
from the abdominal ganglia and innervate the five pairs of gills. 
From the fore-brain a median olfactory nerve (9) and two lateral ones (8) pass 
forward to the olfactory organ; a median eye-nerve (2) passes anteriorly and 
haemally upon the right of the proventriculus (3) to the median eyes ; and a pair 
of lateral eye-nerves pass to the lateral eyes (15). 
The first haemal nerve, or lateral nerve, follows the general course of the lateral 
eye-nerve, but continues posteriorly far back on to the neural side of the abdomen. 
The haemal nerves of the hind-brain radiate from the brain to the margins of the 
carapace, and each one passes anterior to the appendage of its own metamere. 
The integumentary portions divide into haemal and neural branches, of which the 
haemal branches (5) are cut off. Each haemal branch gives off a small nerve which 
turns back toward the median line upon the haemal side of the body. 
The haemal nerves of the accessory brain pass through the occipital ring to the 
sides of the body between the operculum and the sixth cephalothoracic appendage. 
The seventh innervates the posterior angles of the cephalothorax, the eighth the 
opercular portion of the abdomen. The next five haemal nerves arise from the five 
branchial neuromeres, pass out anterior to the gills to the sides of the abdominal 
carapace, and innervate the first five spines upon the sides of the abdomen. 
The first post-branchial nerve innervates the last abdominal spine ; the second 
post-branchial nerve and one branch of the third post-branchial innervate the 
posterior angles of the abdomen and the muscles of the telson; and the caudal 
branch of the third post-branchial nerve innervates the telson. 
Intestinal branches arise from all the haemal nerves from the sixth to the 
sixteenth, and pass to the longitudinal abdominal muscles and to the intestine. 
Cardiac nerves arise from all the haemal nerves from the sixth to the thirteenth. 
Six of the cardiac nerves communicate with the lateral sympathetic nerve (24), 
which innervates the branchio-thoracic muscles (16). 
Two post-cardiac nerves arise from the first two post-branchial nerves, and passing 
to the haemal side anastomose with a branch from the last cardiac nerve, and inner- 
vate the extensors (27) of the telson and the epidermis behind the heart. 
1, Cephalothorax ; 2, median eye-nerve ; 3, proventriculus ; 4, tergo-proplastral 
muscles ; 5, haemal branch of integumentary nerve ; 6, entocoxites ; 7, 2nd haemal 
nerve ; 8, right olfactory nerve; 9, median olfactory nerve; 10, intestine; 11, 
endosternite ; 12, fore-brain; 13, origin of 4th neural nerve; 14, lateral nerve ; 
15, lateral eye; 16, branchio-thoracic muscles ; 17, external branchial muscles ; 
~ 18, tendinous stigmata; 19, branchial cartilages; 20, intestine; 21, abdominal 
endochondrites ; 22, ventral cord; 23, haemo-neural muscles; 24, lateral sym- 
pathetic nerve ; 25, occludor ani; 26, sphincter ani; 27, extensors of telson; 28, 
anus ; 29, flexors of telson; 30, lateral projections of abdomen; 51, nerves of 
spines ; 32, external branchial muscles. 
VO lites IVs ap 
