6 BULLETIN OF THE 
formed (Fig. 10). Finally, in the adult, the nucleus of the cell, which 
has been pushed centripetad by the multiplication of fibrillee, comes to 
lie opposite several pairs of radial rows or sheets of fibrille. These 
sheets always occur in pairs, the components of the pairs being separated 
by a narrow clear space, and the pairs by broader spaces. 
As I have said, this musculature occurs throughout the entire stalk up 
to the base of the calyx (Plate III. Fig. 19, mw.). I do not understand 
on what ground Ehlers states (90, p. 146) that in Urnatella “der 
Muskelmantel in den gleichmässig dicken Stengelgliedern nicht deren 
ganze Lange erfiillt.” 
There is a considerable difference between my description of the struc- 
tures of the muscle fibres and that of Ehlers (90, pp. 25-28) for Asco- 
podaria. In the latter case, the muscle cells are placed three to five 
deep, instead of in one peripheral series, as in Urnatella. Moreover, in 
Ascopodaria the fibrille lie in two thick peripheral bands on the sides 
of each muscle cell ; whereas in Urnatella several muscle bands (each 
consisting of a single row of fibrillae) belong to each cell. 
The differences between the two genera are easily explained by assum- 
ing an increase in the number of muscle cells in Ascopodaria, so that 
they can no longer lie in a single peripheral series, and that the fibrille 
bands have become greatly crowded together, so that one band is not 
equivalent to a single band of Urnatella, but to all of the bands of Urna- 
tella which have arisen on one side of the cell. The stalk musculature 
of Ascopodaria is thus more highly developed than that of Urnatella. 
Ehlers mentions the resemblance between the muscle fibres of Ascopo- 
daria and those of Nematodes, especially the Coclomyaria. 
I have referred above to vibratile movements in the living stalk. 
Stained sections show, placed more or less abundantly throughout the 
stalk, elongated spaces terminating blindly at one end in structures 
which must be regarded as flame cells (Plate II. Fig. 12, cl. jim.). 
Such a flame cell is spherical in form, stains slightly, possesses a large 
nucleus, and gives off into the elongated space cl. tb. the well known 
cirrus (Wimperflamme). 
The form of the cirrus in all cases examined was conical, the axis 
of the cone being usually thrown into a sigmoid curve. Where the 
cirrus arises from the cell, it is slightly constricted, then enlarges sud- 
denly, forming a thickened ring. Distal of this ring the cirrus tapers 
gradually toa fine point. That the cirrus is composed of a number of 
agglutinated cilia is indicated by the presence of longitudinal strie. I 
believe that the flame cell closes the lumen of the tubule at this point. 
