PORTER: TRICHONYMPHA. 53 
margin rests on the anterior sloping surface of the outer layer (st.”), 
while the anterior end of the inner layer (st,/) is covered by the expanded 
knob-like portion (tub.) of the protoplasmic core (Figs. 7 and 8). 
The whole of this portion, forming the nipple-like projection of the 
anterior extremity of the animal, is very active in the living creature ; 
it is constantly in motion, turning from side to side, and, as it were, 
nosing its way through the crowd of its associates. 
The axial rod (Figs. 7, 8, ax.) is apparently the only means of union 
between this nipple-like part of the animal and the bell-shaped region, 
for a fissure (Figs, 7, 8, fis.), encircling the base of the nipple, penetrates 
the layers surrounding the axis, thus severing all other connection. 
Behind the fissure, what seem to be continuations of the outer and 
inner layers of the nipple are carried backward over the bell-shaped 
region, i. e. over a little less than one third the length of the animal. 
A middle layer never appears in this region, a fact which makes it seem 
probable that such an appearance in the nipple region is due merely to 
a space between the inner and outer layers. Since the enveloping layers 
are so much alike in the nipple- and bell-shaped regions, I shall not 
attempt to give a separate description of them in each region, but pro- 
ceed at once to state what I have to say about these layers for the 
whole “head” region. 
The inner layer stains only slightly, if at all. From the fissure back- 
ards, as far as it extends, it is marked by fine lines perpendicular to 
the surface. This appearance is due to the cilia, which penetrate both 
the enveloping layers. The same structural condition probably exists 
in front of the fissure, although it was not possible, owing to the small 
diameter of the nipple-like projection (about 6 u) and the thickness of 
my sections (3.3 u), to detect any striations. 
The cilia arise from the granular protoplasm, at the deep surface of 
the inner layer, which they traverse, and thus give a striated appear- 
ance (Fig. 16, st.str.). They are of about the same refractive power 
and stainability as the outer layer, and consequently I have not been 
able to trace them through that layer; but I think that their passing 
through it is hardly questionable. The arrangement of the radial stria- 
tions of the inner layer, which I believe to be due to the cilia, is best made 
out from tangential sections of the bell, where their cut ends appear as 
dots. The dots are placed in quincunx order, much as shown in Fig. 
20. This arrangement gives two series of diagonal rows of dots cross- 
ing each other nearly at right angles and making angles of 45 de- 
grees with the longitudinal axis of the animal. Secondary rows, both 
