153 
MUSEUM OF COMPARATIVE ZOOLOGY. 
any time in the course of manipulation a change to a denser fluid be 
made too suddenly, the result will be to force the partition forward, and 
consequently to bend the cesophagus in the space between the brain and 
the partition, where it is free from supporting tissue. Exactly this is 
shown to have happened, only in a less degree, in my Figure 8. 
Following now the course of the asophageal cell after it emerges from 
the partition into the general body cavity, one finds a second cell along- 
side of it (Plate LIT. Fig. 33, el. in. I.), which resembles it in the entire 
| absence of transverse cell boundaries and in the presence of many nuclei, 
| but is unlike it in the highly granular condition of the protoplasm and 
| inthe shape and appearance of the nuclei. Since the intestine hangs free 
| in the body cavity, the position of the cells can be determined only in 
| a general way. The new cell, which may be named the first intestinal 
cell, lies approximately lateral to the oesophageal cell (Fig. 33). It be- 
gins at about 0.8 mm. from the apex of the head; about 0.4 mm. far- 
ther back, a second intestinal cell (el. in. II., Fig. 34) is added. This 
lies nearly ventral. A third cell (cl. in. III., Fig. 35) begins 1.3 mm. 
from the apex of the head, and a fourth (cl. in. IV., Fig. 36) 0.1 mm. 
farther posteriad. "This completes the number. The osophageal cell, 
which may be recognized by the presence in it of the cross section of 
the chitinous tube, now lies lateral to the four intestinal cells (Fig. 36), 
but soon wedges itself in between two of them until it reaches the centre 
of the group (Fig. 43), and then suddenly ends, leaving a cavity (Fig. 44) 
surrounded by the four intestinal cells which have accompanied it a 
longer or shorter distance from their origin. 
It is now necessary to ask how the chitinous tube is concerned in these 
changes. Up to the point where the fourth intestinal cell is added, it 
remains a straight simple tube. Shortly beyond that point it makes a 
complete turn upon itself (Plate I. Fig. 8), and from a lateral position 
with reference to the four intestinal cells it reaches a median one 
(Plate III. Figs. 37-43).. Hence the loop lies in that portion of the 
esophageal cell which is wedged in between two of the intestinal cells 
(Fig. 38), and almost completely fills the space. The tube proceeds 
a short distance farther, 60 only, tapers to an exceedingly fine point, 
and opens out into the space which has arisen between the four intes- 
tinal cells (Figs. 8 and 44). This space is the intestine proper, and 
justifies the application of the name “ intestinal cells” to those elements 
which, though originating farther forward, were destined to bound it. 
These relations, which are evident in every complete series through this 
region, are represented in a succession of figures taken from one series of 
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