502 PROF. OWEN ON THE ANATOMY 
all forms and grades of Articulata are due to ‘secondary cause or law’ as strongly as 
when I expressed the same belief in regard to the Vertebrata *, and defined it as * the 
deep and pregnant principle in Philosophy " t evolved in the researches on the General 
Analogies and Archetype of the Vertebrate Skeleton. 
* On the Nature of Limbs, 8vo, 1849, p. 86. T Hx p. 10: 
DESCRIPTION OF THE PLATES. 
PLATE XXXVI. 
Limulus polyphemus. 
Fig. 1. Alimentary canal, hepatic ducts, part of the liver, and of the muscular system, in situ, viewed 
above, or from the dorsal aspect. 
A. Cephaletron: a” its postlateral spinous production. 
B. Thoracetron. 
c. Base of Pleon. 
1. Compound eye. 
a 1. Ocelli. 
h. Entapophysial pit of hindmost (by anchylosis) cephaletral segment. 
i. Intestine. 
i 1-4. Entapophysial pits of thoracetron. 
k. Terminal spine of the ocular or medilateral ridge of the carapace. 
|. Anterior hepatic duct. 
m. Posterior hepatic duct. 
m 1-6. Marginal articulated spines of thoracetron. 
n 1-8. Marginal spinous angles of thoracetral segments. 
n. reor 
'. Hepatic lobe, partially injected from the duct. 
0. o. Dilated beginning of intestine. 
s. Stomach. 
.t, t. Fasciculi of ‘ depressores thoracetri’ muscles. 
Fig. 2. Heart and vessels, with parts of ovaria, in situ, viewed from above. 
A, B, C, as in fig. 1 
a. Heart 
6. Part of pericardial sinus. 
b'. Part of pericardial sinus laid open. 
c, €. Ostia venosa. 
e, e. Neural arteries. 
f, f'. Epimeral arteries of cephaletron. 
9, Y”. Epimeral arteries of thoracetron. 
h. Ocellar 
i 1-6. nov pits of thoracetron. 
n. Medilateral vein and sinus of cephaletron. 
o. Oviduct, 
