130 
ORIGINAL ARTICLES. 
According to tlie principles laid down, tlie morphological rela¬ 
tions of the various processes in the first caudal vertebra of JSFaseus 
may be stated thus: that the undivided part and inferior extre¬ 
mity of the transverse process together correspond in greatest 
degree with the transverse processes further forward, inasmuch as 
these portions lie in the primary circle; while the small superior 
part of the bifid extremity of the transverse process, as well as the 
bone which it supports, is a radiation outwards from that circle; and 
the limbs of the inferior arch are radiations or “ actinal elements ” 
(if that term be preferred) directed inwards. The neural arch being 
likewise formed by two radiations, the neural and inferior arches 
are in that respect corresponding structures placed above and below 
the centrum. 
Behind the limits of the abdominal cavity there can be no longer 
any talk of primary rings and radiations. Relation to the visceral 
cavity has ceased, and the processes are correctly grouped according 
to their relations to the bodies of the vertebrae. A tendency is also 
observed to supero-inferior symmetry round the bodies of the verte¬ 
brae, but it is a peculiarity of the tail, and in harmony with the very 
different development of the tail contrasted with that of the trunk. 
Bor the tail is not developed like the trunk from a series of layers 
which fold inwards and form invaginated cylinders, but it is a solid 
projection backwards from certain of the layers, growing out as a 
mesial limb or appendage to the trunk. 
Where the caudal relations are fully established, the inferior 
arches in all animals very evidently correspond, but they are serial 
with very different structures further forwards in different species. 
Thus, in Naseus they are continuous, at the fore part of the tail, with 
vessel-embracing arches internal to the visceral cavity; and only through 
these or through the divided portions of the abdominal membrane do 
they become serial with transverse processes. In Lophius piscatorius 
they are only continuous with imperfect vessel-embracing arches. 
But in the Gadidae they are directly serial with the structures 
bounding the visceral cavity; and in some species, e. g . Gadus bar- 
batus , we find complete rings of great size, terminating in spines, en¬ 
circling the abdominal cavity a considerable way forwards. They 
never, however, enter into typical segments of the body, for they 
never pass in front of the vent, which, though not a primary opening, 
is still morphologically the hinder extremity of the digestive system. 
In Saurians the inferior caudal arches are only in series with 
structures projecting into the interior of the visceral cavity: those 
in the anterior part of the tail so project; and further forwards, 
in series with them, there are, in certain species, imperforate pro¬ 
cesses projecting in the middle line, and not even forking to enclose 
the great vessels. 
Still another arrangement is met with in Menobranchus lateralis . 
In series with the transverse processes of the trunk, there are, in 
the anterior caudal vertebrae, sometimes as many as three pairs of 
