The young escapes from the egg in a form as unlike the parent as can
be imagined. It is a flat ovate body with a long flat tail, altogether
presenting a curious resemblance to the tadpole of a frog. In this
condition I have found the larva of the _Clavelina_, and have followed
it to the development of the _Ascidia_ form. By means of the rapid
vibrations of the powerful tail, the little tadpole swims for short
distances through the water, with more effort than effect. After a
while, it rests; swims again, and again rests; till at last it moves
no more. A coloured eye-speck is visible on the surface, destined to
be absorbed; the tail is beginning to disappear (in some cases it
is separated by a spontaneous constriction at its junction with the
body, in others it appears to be gradually absorbed); one or more
warts are seen budding from the opposite extremity of the body. These
last secrete a cement by which the animal is finally attached to its
support, shell, stone, or sea-weed, either growing out into creeping
and adherent root-threads, or enlarging into a broad base, from which
the body begins to grow upward. After a while the two orifices are
formed; first within, on the mantle, before the exterior test is
pierced; then the internal organs, the gill-sac, and the pulsating
heart, if it be one of the transparent species, become recognisable;
the single eye-speck, a temporary organ, pales and disappears; and
the permanent circles of visual organs are formed around the siphonal
orifices. And thus the Ascidian is developed.