STRUCTURE AND DEVELOPMENT OF LOXOSOMA. 
299 
of certain other Trochospheres (as described below), we obtain 
evidence that the history of the brain in L. Leptoclini is 
really archaic in its general features, and there hence appears 
to be little reason for hesitation in the assumption that the 
larvae of both L. Tethyae and L. pes are degenerate forms, in 
which the sense organs (eyes) and the brain have suffered 
retrogressive modifications. A similar change, though to a 
less marked extent, seems to have occurred in the larva of 
Pedicellina, which in this respect thus shows itself to be less 
primitive than that of L. Leptoclini. 
It has been suggested by Hatschek (14) that the dorsal 
organ becomes the first hud in Pedicellina, the first pair of 
buds in Loxosoma; in order to establish my view of its 
nature, it is necessary to examine the history of the metamor- 
phosis, to ascertain if the larva makes use of its dorsal 
organ as a budding region. This I find definitely to be not 
the case in L. Leptoclini, and the hypothesis of the nervous 
nature of the dorsal organ remains in consequence unshaken 
when the budding processes of the larva are studied. 
My method of obtaining free larvae was to place a large 
number of L. Leptoclini growing on the Ascidian in a glass 
vessel, blackened in every part with the exception of a small 
window facing the light. On covering the top of the vessel 
with a piece of black paper, the larvae, as they were hatched, 
made their way to the only part of the glass whence any light 
was proceeding, and in this position they could be easily detected 
and captured. 
From various causes, and chiefly from the death and conse- 
quent putrefaction of the Leptoclinum within a day or two 
from its removal from the sea, the number of the larvae which 
I succeeded in observing during the process of their metamor- 
phosis was very small. In no single case did I observe any 
permanent fixation of the larva, but the method of the fixation, 
if this really takes place normally, is perhaps not of very great 
importance. If, as is probable, the normal resting-place of 
the larva is on the surface of the Leptoclinum which bears 
the adult individuals, the dying condition of the Ascidian in 
