M. Koidzumi 
263 
more deeply, just as in the inner layer of the nipple and the bell of Tricho¬ 
nympha. The outer surface takes dyes intensely, and shows an appearance 
of an aggregation of minute and very deeply stained granules, indicating 
that the flagella arise therefrom. Thus it seems probable that the rind is the 
homologue of the inner layer of the head of Trichonympha and Pseudotricho- 
nympha. The conical core and the contents of the space around it stain more 
or less deeply. The outer surface of the cone, and the vertical partition con¬ 
necting it with the inner wall of the tubular rind also stain deeply, but no 
granular appearance is there visible. Differential staining of the inner and 
outer cones of the core at their apices is not easy, but the outer seems to 
stain a little more faintly. 
The peripheral part of the head is identical in structure with the outer 
layer in the anterior region of Trichonympha. It is closely traversed by 
flagella, which arise at the junction with the central axis. Owing to the 
flattening of the head, the proximal ends of the flagella embedded in the 
peripheral layer are very long, so that their distal or free ends are nearly 
equal to the embedded portions in length. The flagella are shortest anteriorly, 
and gradually increase in length posteriorly: the longest ones measure 20-25 /x, 
including the embedded portion. Behind the head, a thin but distinct layer 
is noticed lining its concave surface. The flagella do not arise from this layer, 
but run parallel to it. 
The anterior surface of the whole axis is apparently naked, and provided 
with no special structure, such as the cap on the nipple in the preceding 
genera. Careful observation, however, shows that there is a thin membrane 
lying on the frontal surface of the head—this membrane being hardly notice¬ 
able, owing to the absence of any space between it and the frontal surface. 
In vigorous animalcules the head is either swung actively from side to 
side, or is held straight and the axial column alone displaced backwards and 
forwards along the long axis of the body. In the former case, the shape of 
the head becomes markedly asymmetrical; in the latter, the central portion 
of the head is alternately drawn in and pushed out in rapid succession. 
From the above descriptions, it will be recognized that the head of this 
form is homologous in organization with the anterior region of Trichonympha 
and Pseudotrichonympha. As already indicated, the peripheral part traversed 
by the flagella, and the tubular rind of the axial column, are respectively 
comparable with the outer and the inner layers of the anterior part of Tricho¬ 
nympha . It seems probable also that the conical core and the inner conical 
body, at its anterior or basal end, are homologous respectively with the 
columnar axis, and the ball at its anterior end, in the nipple of Pseudotricho¬ 
nympha. As regards the contents of the space between the outer cone and 
the tubular rind, comparative studies of allied forms afford strong evidence 
that it is homologous with the contents of the axis of the nipple in Tricho¬ 
nympha. A discussion of the nature of these structures will be given in detail 
in Part II. 
