File:Two Melicerta tyro Wellcome M0016981.jpg

The illustration shows two Melicerta tyro, the discovery of which Charles Thomas Hudson describes in the paper. https://www.biodiversitylibrary.org/item/49866#page/189/mode/1up The trochal disk was oval, with a gap in it on the side opposite to the mouth. Two parallel rows of cilia—the upper large, the lower small—ran round the edge of the disk separated by a groove which led down into the mouth (Fig. 1,a); and the lower row of cilia were continued round the edges of the mouth after the usual fashion in Melicertans. But what struck the eye at once was the long flexible antenna. When the creature was withdrawn into its tube the antenna generally projected above it like a thin wand. It was turned too to a curious use; for when Cephalosiphon had made up its mind to emerge from its retreat, it hooked its antenna (see Fig. 1, b) over the side of its tube, and getting a good purchase, hoisted up its body into a great curve, and then letting go its grip of the case, unbent itself, and at once unfolded its disk.
Close to a large cluster of the tubes of Archimedea remex (a new infusorion, to be described lower down) was a very tiny tube, barely the 1/400, of an inch long, and out of which protruded a wheel-animal (Fig. 1, c) Plate CXVII., about 1/200 of an inch in length, and like a Cephalo- siphon only with a hump instead of the characteristic antenna. I isolated the creature and kept it under daily observation for nearly a fortnight, and during that time had the pleasure of seeing it grow rapidly into the form of an adult Cephalosiphon (Fig. 1, a). In twenty-four hours the hump had developed into a short antenna ; in four days the young Cephalostphon had grown from 1/200 of an inch to 1/80 in six days to 1/65; in twelve days to 1/55.
When inside the tube the animal is extended to its full length as in Fig. 2, where a is the ciliated front down which a groove ciliated on both sides leads to the entrance of the mouth d. On protruding from its home it first remains straight quivering its cilia: then, if not alarmed by any shake, or by any- thing passing, it thrusts quite half its body from its tube, and twists it up into the screw-like form seen in Fig. 3.

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Keywords: Protozoology