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Transactions of the Boyal Society of South Africa. 
postcaval of the adult ; the other curves round the liver and breaks up 
into numerous hepatic portal capillaries after receiving the right posterior 
cardinal. The tadpole thus dilfers from the adult in having the hepatic 
portal connected with the postcaval. 
Arterial System. — Eeference to Fig. 7 will show that there are vestiges 
of four arches : one passing upwards between the hyoid and the first 
branchial bars and three associated with the three gill-slits. Another, 
apparently aortic, arch passes through the slit I, but, as already 
mentioned, this slit cannot be held to be a gill-slit. The three internal 
gill-pouches are supplied with blood by all the arches except the second, 
i.e. the systemic, and the arrangement of the arteries to these pouches 
seem to have no significance, for A6 goes to the second pouch ; Al, A2 first 
to the second then on to the first ; A3 to the second ; A4 and A5 to the 
third. Anyway, it will be seen that the internal gill-pouches are very 
copiously supplied with blood, so that we may consider them as important 
if not the sole respiratory organs. 
Of the four arches only the second is connected to the dorsal aorta ; 
but also the third, in younger individuals, would most probably have such 
a connection through A5. 
The Nervous System. — The following cranial nerves were found : — 
1. The olfactory, branching to the olfactory sacs and to Jacobsohn's 
organ. 
2. The optic, to the eye. Anteriorly the pituitary body is con- 
tinued as a laterally expanded, hollow, ventral outgrowth from the 
diencephalon ; the optic nerve from each side is joined to this outgrowth 
on the same side, so that there is no crossing of the optic fibres to form a 
chiasma. 
3. The oculomotor, leaving the brain just behind the pituitary body, 
receives a branch from the trochlearis as it leaves the cranium and goes 
to eye muscles. 
4. Just in front of the auditory capsule there is a large ganglion 
which is joined (?) to the diencephalon just in front of the optic lobes. 
Distally the ganglion is continued into the following seven nerves : — 
{a) The trochlearis, with a branch to the oculomotor and another to 
the muscles of the eye. 
{b) The trigeminus : (a) one branch along the ventral surface of the 
pterygoid and into the muscle which joins Meckel's cartilage to the pala- 
tine portion of the palato-pterygo-quadrate bar ; (/3) another branch to the 
epithelium of the roof of the mouth. 
(c) The abducens, running along the dorsal surface of the pterygoid 
just ventral to the internal jugular vein and going to a ventral eye 
muscle. 
{d) The facial, with the following branches : (a) running over the large 
