4 BULLETIN OF THE 
An optical longitudinal section of the living stalk (Plate I. Fig. 7) 
shows that it consists of a thick cuticula, within which is a mass of ill- 
defined tissue. The cuticula is thicker and more opaque in the basal 
segments, thinner and more transparent in the distal ones. Each of the 
basal segments often contains a mass of globular, highly refractive bodies, 
which may be forced out from the segment by crushing the latter (Plate 
I. Figs. 4, 5). Isolated by this means they are seen to be of the most 
varied size, and to resemble yolk spherules. Besides these granules, one 
finds lying near the cuticula in all but the oldest segments a fibrillated 
layer consisting of elongated, spindle-shaped, highly granular cells in the 
midst of the yolk spherules (Plate I. Fig. 7), and, finally, one or several 
flickering bodies reminding one by their motion of the cirri! of flame 
cells. In the dark zones optical sections reveal indications of a transverse 
septum. 
A more accurate insight into the histological structures is gained 
from thin sections of the stalk. 
The cuticula appears in two conditions, which are not sharply separated, 
but pass into each other through intermediate conditions. The one 
kind (Plate I. Fig. 4, cta.) occurs in the middle zone of each segment. 
It is transparent and flexible, and becomes thicker in passing from the 
distal to the proximal segments. It stains in hematoxylin, and is then 
seen to be composed of laminz, for it appears in section distinctly 
striated (Plate I. Fig. 4; Plate II. Fig. 16). The other kind of cuticula 
occurs chiefly at the constrictions between segments, but it extends over 
the two ends of the segments also, and even over the middle zones of 
the segments, as an outer cuticula (Plate II. Fig. 8, cta’.). It forms, 
moreover, the septa between adjacent segments. It does not stain in 
hematoxylin, is more highly refractive than the first kind, and has a 
yellowish color by transmitted light. Where it passes over into the first 
mentioned kind of cuticula, it becomes distinctly striated, and gradually 
loses its specific characters, gaining those of the first kind, of which it is 
probably only a modification. It is the presence of these two kinds of 
cuticula that causes the superficial appearance of alternating light and 
dark zones on the stem. These two kinds of cuticula do not correspond 
to the inner and outer cuticulas which Ehlers (’90, pp. 16, 17) describes 
for Ascopodaria. Two layers with the characters of those of Ehlers ap- 
pear not to exist in Urnatella. 
The ectoderm (Plate II. Figs. 11, 10, 16) diminishes in thickness from 
1T employ the word “cirrus” in the sense in which it is used by Biitschli 
for Ciliata (cf. Bronn’s Thierreich, Protozoa, p. 1324). 
