No.1.] ZTHE DEVELOPMENT OF BALANOGLOSSUS. 9 
small crescentic pigment spots or eyes. At the four corners 
of the apical plate are seen entering the four portions of the 
anterior ciliated band. At this stage the apical plate absorbs 
the ciliatic bands of the two sides, inasmuch as the bands are 
not after entering differentiated from the plate. 
If we turn now to the internal structures, we find a rela- 
tively small digestive tract in the center of the body; it is 
divided into three parts, — oesophagus, stomach, and intestine. 
The three are separated by constrictions, and while in the 
larva the stomach and intestine are separated by a diaphragm- 
like partition, pierced in its center, this disappears in later life, 
and we have formed a stomach-intestine. The intestine opens 
by a small opening in the posterior plate; this is not in the 
center, but lies in the middle line nearer to the dorsal side of 
the larva. 
A delicate thread of tissue runs from the under and 
inner surface of the apical plate to near the anterior end of 
the stomach; sections show it is part of the anterior body- 
cavity. In surface views this anterior body-cavity was not 
seen ; sections show it to be a thin-walled tube that opens at 
the surface of the larva near the mid-dorsal line. 
The next stage is shown in Fig. 2; Pl. I. This presents 
approximately the same surface to the observer, but somewhat 
more of the dorsal area is seen, and correspondingly less of the 
ventral side. The larva has increased in size, but the general 
shape is muchas in the preceding stage. The anterior ciliated 
band follows in general the same course as before. An inter- 
esting change has taken place in the number of its tentacular 
processes ; these have increased in each group from nine to 
thirteen, the additional processes having presumably been 
added at both ends of each group. At the twelve ends (on 
each side) the band shows a tendency to form new folds; and 
in this way, no doubt, the number of tentacles is increased. 
It is interesting to note that the increase in number of 
new tenacles is the same in each of the six (on each side) 
groups. 
Within the circum-oral area are still found the large pigment 
spots. 
