These polypes form a group resembling a cluster, or more properly an open flower; this flower or cluster is supported by a stem, which is fixed by its lower extremity to some of the aquatic plants or extraneous bodies that are found in the water; the upper extremity forms itself into eight or nine lateral branches, perfectly similar to each other; these have also subordinate branches, whose collective form much resembles that of a leaf. Every one of these assemblages is composed of one principal branch or nerve, which makes with the main stem of the cluster an angle somewhat greater than a right one; from both sides of this nerve the smaller lateral branches proceed; these are shorter the nearer their origin is to the principal branch.
At the extremity of the principal branch, and also of all the lateral ones, there is a polype or vorticella. There are others on both sides of the lateral twigs, but at different distances from their extremity. These polypes are all exceeding small, and of a bell-like figure; near their mouth a quick motion may be discerned, though not with sufficient distinctness to convey an adequate idea of its cause; upon the branches of these clusters are round bodies, which will be more particularly described presently.
Every cluster has eight or nine of these branches or leaves; they do not all proceed from the same point, but the points from whence they set out are not far asunder; each of these branches is bent a little inwards, so that all of them taken together form a kind of shallow cup. If the eye be placed right over the base of this cup, the appearance of the whole eight or nine branches is like unto that of a star, with so many rays proceeding from the center. If the cluster be slightly touched, all the branches instantly fold up, and form a small round mass. The stem which supports the cluster contracts also at the same time, folding up like a workman’s measuring rule, that consists of three or four joints. This extraordinary assemblage constitutes one organized whole, formed of a multitude of similar and particular ones. A new species of society, in which all the individuals are members of each other in the strictest sense, and all participate of the same life.
A few days after one of these clusters is formed, small round bodies or bulbs may be perceived to protrude in several places from the body of the branch; these grow very fast, and arrive at their greatest growth in two or three days. The bulbs detach themselves from the branches out of which they spring, and go away, swimming till they can settle upon some substance which they meet with in the water, and to which they fix themselves by a short pedicle; the bulbs are then round, only a little flatted on the under side, the pedicle continues to lengthen gradually for about twenty-four hours, during the same time the bulbs also change their figure, and become nearly oval. There are in a cluster but few of these bulbs, compared with the number of the vorticellæ, neither do all the bulbs come out at the same time. The bulb then divides lengthways into two smaller ones, but which are still much larger than the vorticellæ themselves. It is not long before these are separated like the first, and thus form four bulbs on the same stalk; these again divide themselves, and form eight; which again subdivide, and consequently make sixteen. They are all connected with the stalk by a proper pedicle, but they are not all of an equal size; the largest continue to divide, and the smallest begin to open, and take the bell-formed shape. Trembley observed from one round bulb, in about twenty-four hours, by repeated divisions, one-hundred and ten vorticellæ to be formed.
It has been asked with propriety, what plant or what animal could have led us to expect an existence and mode of propagation similar to that of the vorticella anastatica?
Fig. 13 represents one branch of the vorticella anastatica; on this branch, besides the vorticellæ which are of a bell-like form, some of those round bodies from which they first spring, and by which they are so remarkably distinguished from any other species, may be seen.
Fig. 14 represents one of the globular bodies after it has parted from the cluster, and has fixed itself to some other body, and after the globule itself and its pedicle have begun to lengthen.
Fig. 15 represents the two bodies that were formed by the parting of that which is shewn at Fig. 14.
Fig. 16* represents four that were formed by the separation of the two bulbs, exhibited in the foregoing figure.