475 
and agrees with Perophora in the total absence of an epicardium 
such as VAN BENEDEN and JULIN describe, and also in the absence of 
an abdomen; in other words the digestive tract does not lie behind 
the pharynx but almost entirely on the left side of the latter. But 
it is distinguished from both of these genera by the presence of 
perfect internal non-papillated longitudinal bars in the walls of the 
branchial sac. ; 
The bud-development is strikingly like that of Perophora 
although no rotation or displacing of the inner vesicle occurs, as has 
been described in the latter. 
In members of this family it is well known that the buds arise 
on a proliferous stolon which grows out from the base of the larva 
during the metamorphosis. This is also true of Ecteinascidia, 
and as in all other Ascidians, the bud-rudiment consists of two simple 
vesicles, one within the other. The outer or ectodermal one is derived 
directly from the ectoderm of the stolon and the inner or endodermal 
vesicle from the stolonic cloison or septum. The latter structure, however, 
cannot in truth be called a septum at all, as it is nota flat double-walled 
partition, as in Perophora, extending across the lumen of the 
stolon and dividing it longitudinally into two compartments or sinuses; 
but it is a tube lying inside the ectodermal wall of the stolon, and is 
bathed on all sides by the blood. 
In Ecteinascidia the axial relations of the bud and stolon are 
quite different from those which occur in Perophora. In the latter 
the bud is connected with the stolon on its ventral side which lies 
parallel with the long axis of the stolon, while in Ecteinascidia 
the connection is at the extreme posterior end of the bud which stands 
up at right angles to the stolon, as in Clavelina. 
At the point where a bud is to be formed, the ectoderm of the 
stolon thickens and becomes raised up into a knoblike protuberance 
into which the inner stolonic tube sends a much thickened evagination 
to form the primitive inner vesicle. The bud-rudiment elongates ina 
direction perpendicular to the stolon, and its free end becomes the 
anterior end of the bud, the stolonic connection being posterior as 
stated above. The right and left sides are parallel with the stolon, and 
in all the cases I have observed the ventral surface of the bud faces 
toward the growing tip of the stolon. 
A section at a very early stage shows that the right side of the 
inner vesicle towards the posterior end has become much thickened, 
and many cells in this region are wandering out to give rise to an 
extensive mass lying on the outside and reaching from the dorsal to 
