368 THE LIVING ANIMALS OF THE WORLD 
has a distinct throat-opening, two rhythmically contracting cavities fulfilling a respiratory 
function and a complex reproductive nodule, or nucleus. Compared with a host of its kindred, 
this animalcule is a giant, the longest diameter of many of the smaller varieties measuring 
no more than the %oooth part of inch, or even less. 
The elegant little BELL-ANIMALCULE, with its crystal wineglass-shaped body, crown 
of vibrating hairs, and long spirally contractile foot-stalk, is a familiar object to the 
possessor of a microscope. Most commonly these single-celled organisms, like the single- 
celled elements of organic tissues, multiply by repeated sub-division, the number that 
can be reproduced in a short space of time by this simple process being almost 
incredible. As many as a million, it has been calculated, of some species may be 
thus derived from an original single individual within twenty hours. In this connection 
these lowly organisms can among living animals most logically lay claim to immortality. 
The individual, in point of fact, never dies. Finding itself growing old and obese at 
the ripe age of, say, sixty minutes, it has simply to split itself up into two offsets, 
which swim away and repeat the process. Occasionally, for the rejuvenescence of the 
race, two individuals coalesce completely with one another, and multiplication by splitting 
takes place. 
Some near relations of the little bell-animalcule, while sub-dividing so far as their bodies 
are concerned, remain united by their foot-stalks, and thus in time build up beautiful tree- 
like structures, laden as it were with crystal bells or fruit. In some of these the common 
branching foot-stalk is erect and rigid, while in others it is flexible, and contains, as in the 
ordinary species, a central elastic ligament. Under these circumstances the whole tree-like 
structure, with its crystal bells, collapses and expands again under the slightest stimulus, and 
constitutes one of the most 
beautiful objects that can be 
viewed through the microscope. 
In lower forms of the 
infusorial animalcules one or 
more long, lash-like organs take 
the place of locomotive hairs. 
In this category are included 
the COLLAR-BEARING ANIMAL- 
CULES. Some of these build 
up tree-like growths by re- 
peated subdivisions and im- 
perfect separation, after the 
manner of the bell-animalcules, 
while others excrete tubular 
dwelling-cases, inhabited by 
the resultants of the splitting 
process. Such forms can with 
difficulty be distinguished from 
skeletonless sponges. 
The animalcule Nocti- 
LUCA, which by its countless 
myriads is the chief constituent 
of ocean phosphorescence, is a 
member of the Lash-bearing 
group. This noteworthy form 
Photo by W, Saville-Kent, F.Z.8.] [ Milford: on-Sea 
CUP-SPONGES, PHOTOGRAPHED AS GROWING as a arr 4 
IN A CORAL_POOL invites a somewhat more 
The Neptune’s-cup Sponge, allied to this species, is sometimes 2 or 3 feet in height extended notice. It is to the 
and diameter presence of the Noctiluca in 
