1880. ] Development of Amphioxus lanceolatus, gi 
grows forward (Fig. 3, Pl. 11), gradually pushes its way along the 
side of the pharynx (Fig. 3, Pl. 1), and becomes the asymetrical 
liver of the adult. 
As the liver passes forward around and along one side of the 
pharynx, that portion of the ventral tubular vessel of the blood 
system which passed beneath it becomes stretched out into a 
peripheral ventral and dorsal vessel for this organ, so that there 
is, so far as can be made out, no connection between the intestinal 
and pharyngeal portions of the ventral vessel, except by way of 
this extension which outlines the liver. In Fig. 5, Pl. 1, the liver 
enlargement is represented at about the time it begins to form, 
and the ventral vessel is seen to conform to the outline of its 
lower edge. 
A second vessel is also represented, which first appears about 
this time, extending from the cartilaginous base of the pharynx, 
between the branchial arches and the pharyngeal ring, upwards 
and backwards to the ventral aspect of the notochord, where it 
becomes lost to view. This vessel is the aortic arc or ductus Bo- 
talli, and with the exception of this arc and the ventral vessel, 
with its hepatic continuation and the swellings at the bases of the 
branchial arches, no portion of the blood system can be made out 
in the living, young or adult animal. At this period the bran- 
chial arches are seven in number upon either side of the 
pharynx, the third and fourth from the anterior end being largest, 
: andare very broad and well defined, with very large spaces between 
their broadly pointed bases, and the stomach is seen just over 
the branchioporic depression, and extends forward into the enlarge- 
ment caused by the swelling-out of the alimentary tract for the 
liver væcum, and in fact this enlargement, and also this section of — 
the alimentary tract after the farther growth of the liver, seems to 
form a very important part of the stomach, and the swaying, 
twisting mass of food, with the accompanying oblique arrange- 
ment of the cilia, generally extends from the posterior limits of © 
the cesophagus to the. beginning of the intestine. The advanced _ 
State of the mouth cavity and the tentacles upon the pharyngeal oe 
Ting will also be noticed in this figure. From the condition as _ 
shown in Fig, 1, Pl. u, the posterio-dorsal, or left, and the ve 
tral, or right edges of the mouth cavity gradually work downward 
and forward until the ventral edge nearly coincides with the ven- 
"al edges of the anterior portion of the body, by 
