An interesting observation which may be useful to our readers was reported sometime ago in Microkosmos.
A Physa-snail had accidentally fallen on the floor and its shell had broken. It was picked up and thrown into a battery-jar aquarium where debris and half dead plants kept company with Vorticello - and - Carchesium colonies. After the lapse of a few days the snail was taken out and found completely overgrown with colonies of Carchesium. Now a dozen Physa-snails was provided with damaged shells and thrown into the jar to see if the broken shell could really do the work. After a week's time, they all were thickly covered with Carchesium and all snails appeared to be in best of health except one that had passed out. The experiment was repeated several times, always with the same result, even in an aquarium where Carchesium was not known to be present.
Having thus procured some fine Carchesium cultures let us have a closer look of the animals. This, after all, was the purpose for which we have gone to the trouble of breeding such household pets. Under the microscope we note that they have the appearance of a flowering tree, completely alive. Every bell-flower is whirling and all the branches are swaying or jerking, making the water around them churn.
At the tip of each branch, a bell-shaped infusoria is attached and more than a hundred animals may thus be together in symbiotic partnership. When disturbed each animal separately will contract his branch into a spiral of one and one-half turn. If the stimulus is very strong, the whole tree will contract at once. Carchesium is distinguished from all other tree-like infusoria-colonies by this ability to contract its branches separately and individually.
The bell-shaped body is supported on a stalk. In the trough-shaped opening is located a lid, the Peristom, the edge or lip of which is carrying two rows of Cilia; these are usually in full activity churning food and water into the interior of the bell. The cilia-edged lip is continued as a spiral into the body with the only change that the outside row of Cilia is converted into a membrane, which forms a funnel-shaped vestibule at the end of which the mouth is located. The actual mouth is hence inside the body and directly connected with the protoplasm. From this mouth food is introduced into a small sac which when full cuts itself loose from the vestibule. At times, one may observe several such ball-shaped sacs or food-vacuolae floating about inside the body until the food is digested. The undigested parts are again eliminated into the vestibule from which they are emptied to the outside by action of the membrane.
Because water is taken in simultaneous with food, we also find present an organ serving as a kidney, this is the contractile vacuole.
Excess water and unused juices are eliminated by a rhythmic contraction and swelling of the vacuole, not unlike the pulsation of a heart. Besides these organs we also note the large U-shaped nucleus which together with the small nucleolus are, so to speak, housing the "soul of it all".
The stalk is hollow and contains a thin muscle thread which in the bell is split up into a bundle of fine fibres. When stimulated, the animal is, thereby, able to contract itself into a small ball simultaneous with the stalk being coiled up like a corkscrew and the animal thus brought out of a danger region. By the stalks elasticity it is again stretched out. This never-ending play of jerking, stretching, whirling and swaying hither and yon of an animal tree with so many animals, is a sight which it is difficult to cease looking at. It is an added enjoyment to realize that these animals are so small that they are only observable under the microscope. In spite of their smallness they achieve their object in life wonderfully well. The water between them and their surroundings is inconstant whirling and churning motion, seizing everything in its giddy whirl; small algae, bacteriae and animaculae thus become defenseless prey and add to satisfy their always present hunger.
Much is still to be learned about these queer colony forming animals. Anyone interested in microscopy and of diligent intellect can do much to promote further knowledge about them. Prof. A. Koeppel has a fine paper in Mikrokosmos XI p.62: 'Die Koloniebildenden Peritrichen' from which some of the above information has been translated.