1897] wee Zoology. 537 
along the neck they project considerably over the general level, and 
seem to be covered only by the cuticula. The anus has its constant 
place, but is marked by a slight irregularity of the surface only for a ` 
short. while after the waste ball is ejected. 
- The animal lives, as a rule, in a cavity of some plant, a living or 
dead leaf, ete., from which it projects, straight, or curved, at any suit- 
able angle. Very often this dwelling is extended forward by the ad- 
dition of a tube (fig. 1, ¢) built by the animal itself with small particles 
of different materials carried along by the current, connected, prob- 
ably, by some mucus secreted from the body. Sometimes these tubes 
are rather hyaline and transparent, containing few foreign bodies. 
Occasionally a specimen is seen in a tube made up entirely by itself. 
From the cavity or tube, the anterior part of the body is projecting, 
when extended, to a short distance behind the peristome-angle (usually 
less so than in fig. 1), while the posterior part is, as a rule, not or very 
indistinctly visible. 
en the animal is emerging from the tube, its anterior part is quite 
straight, the adoral cilia along the ventral side laid together, directed 
. backward, and resting or vibrating very slightly, as a rule (fig. 4). 
Then, all at once, they spread out and begin vibrating vividly, and at 
the same time the anterior processus suddenly turns into the corkscrew- 
shape, like a spring. Thus extended the animal will keep for a shorter 
or longer time, in the way of Vorticellide, often swaying to and fro, or 
turning around its axis, and then as suddenly it will retreat deep into 
its cavity, where it may remain for a few seconds, or minutes, up to 
several hours, and sometimes probably more. At times an animal may 
be seen slowly advancing in its tube, about to the aperture, then 
slowly retreating, and continue doing so for a good while, with the 
cilia, especially the posterior adorals, slightly vibrating. Possibly this 
is done for the purpose of respiration. 
As already stated, there is considerable variation in size. Each in- 
dividual is growing, but slowly, even with abundance of food. With 
the growth of the animal is connected a considerable increase in the 
number of adoral cilia, as well as probably of some other groups. This 
is a fact not sufficiently noticed, so far, as to my knowledge, and with 
it we meet a question of highest interest concerning not only the form 
under consideration, but all Oxytrichidee and related groups.’ It is 
‘Tt should be borne in mind that in Oxytrichide, Euplotide, Halteria, etc., in 
the Heterotricha of Stein, in Amphileptus and some others (which should range 
with the Heterotricha), the adoral zone does not consist of a spiral or longitudi- 
nal series of single cilia, but of transverse rows of such, each one in the shape of 
