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A Series of Lessons in Gnani Yoga826
of easy movement. Differing in shape and appearance as do the numerous
members of the sub-family of vertebrates, still their structure is easily
seen to spring from a single form—all are modifications of some common
pattern, the differences arising from the necessities of the life of the animal,
as manifested through the desire and necessities of the species.
Science shows the direct relationship between the Vertebrates, and the
Invertebrates by means of several connecting-links, the most noticeable of
which is the Lancelot, a creature resembling the fish-form, and yet also closely
resembling the lower (invertebrate) forms of life. This creature has no head,
and but one eye. It is semi-transparent, and possesses cilia for forcing in the
water containing its food. It has something like gills, and a gullet like the lower
forms. It has no heart, the blood being circulated by means of contracting
vessels or parts. Strictly speaking, it has no back-bone, or vertebra, but still
Science has been compelled to class it among the vertebrates because is
has a gristly cartilage where the back-bone is found in the higher forms.
This gristle may be called an “elementary spine.” It has a nervous system
consisting of a single cord which spreads into a broadened end near the
creature’s mouth, and which may therefore be regarded as “something like
a brain.” This creature is really a developed form of Invertebrate, shaped like
a Vertebrate, and showing signs of a rudimentary spine and nervous system
of the latter. It is a “connecting-link.”
The lowest forms of the true Vertebrates are the great families of Fishes.
These Fish families include fishes of high and low degree, some of the higher
forms being as different from the lowest as they (the highest) are different
from the Reptile family. It is not necessary to go into detail regarding the
nature of the fish families, for every student is more or less familiar with
them.
Some peculiar forms of fish show a shading into the Reptile family, in fact
they seem to belong nearly as much to the latter as to their own general
family. Some species of fish known as the Dipnoi or “double-breathers,” have
a remarkable dual system of breathing. That is, they have gills for breathing