414 
BORKR. 
from tlie simplest and almost rudimental condition in which it 
exists in the Myxine and the Lamprey, to that of the most 
perfect of the osseous tribes. Its condition in the former of 
these animals presents a close analogy with some structures that 
are met with in the molluscous, and even in annulose animals. 
So near is the resemblance of the spinal column of the Mjesine, 
more especially, to the annular condition of the framework of 
the Vermes (worms,) that doubts have often arisen whether 
that animal ought not to be ranked among this latter class; for 
in place of a series of bones composing the vertebral column, 
it has merely a soft and flexible tube of a homogeneous and 
cartilaginous substance, exhibiting scarcely any trace of division 
into separate rings, but appearing as if it were formed of a 
continuous hollow cylinder of intervertebral substance, usurping 
the place of the vertebrae, which it is the usual office of that 
substance to connect together, and having in its axis a continuous 
canal filled with gelatinous fluid. The nervous cord is on the 
outside of this column, and the cartilage forms no canal for 
its passage and protection,” as is formed by bony processes in 
the higher orders of fishes. “The nervous matter here consists 
merely of two slender cords, which run parallel to each other 
in a groove on the upper part of the spinal column; and 
these cords are only covered by a thin membrane, the presence 
of which it requires very minute attention to detect. As we 
ascend from this rudimental condition, which resembles that of 
the cuttle {sepia,) we find it in the Lamprey more distinctly 
divided into rounded portions, which appear like beads strung 
together, or like rings with a canal throughout the whole. 
There is also a skull to hold the brain, which, as in other 
fishes, does not fill the cavity, which on either side contains 
a considerable space that is occupied with an organ of hearing; 
but while there are nerves from the brain, as in other fishes, 
that important portion of the brain, the cerebellum, is absent.” 
Ekstrom says that the colour of this fish is greyish flesh- 
colour wlien alive. 
