Darwin, who examined some of these creatures very minutely, tells us that "several genera" (Flustræ, Escharæ, Cellaria, Cresia, and others) agree in having singular movable organs attached to their cells. The organs in the greater number of cases very closely resemble the head of a vulture; but the lower mandible can be opened much wider than a real bird's beak. The head itself possesses considerable powers of movement, by means of a short neck. In one zoophyte the head itself was fixed, but the lower jaw free; in another it was replaced by a triangular hood, with a beautifully-fitted trap-door, which evidently answered to the lower mandible. In the greater number of species each cell was provided with one head, but in others each cell had two. [Illustration: Fig. 59. Corpuscles from which originate the Polypidom.] [Illustration: Fig. 60. First form of the Polypidom. (Lacaze-Duthiers.)] "The young cells at the end of the branches of these corallines contain quite immature polypi, yet the vulture heads attached to them, though small, are in every respect perfect. When the polypus was removed by a needle from any of the cells, these organs did not appear to be in the least affected. When one of the vulture-like heads was cut off from a cell, the lower mandible retained its power of opening and closing. Perhaps the most singular part of their structure is, that when there are more than two rows of cells on a branch, the central cells were furnished with these appendages of only one-fourth the size of the outside ones. Their movements varied according to the species; but in some I never saw the least motion, while others, with the lower mandible generally wide open, oscillated backwards and forwards at the rate of about five seconds each turn; others moved rapidly and by starts. When touched with a needle, the beak generally seized the point so firmly that the whole branch might be shaken." In the _Cresia_, Darwin observed that each cell was furnished with a long-toothed bristle, which had the power of moving very quickly; each bristle and each vulture-like head moving quite independently of each other; sometimes all on one side, sometimes those on one branch only moving simultaneously, sometimes one after the other. In these actions we apparently behold as perfect a transmission of will in the zoophyte, though composed of thousands of distinct polyps, as in any distinct animal. "What can be more remarkable," he adds, "than to see a plant-like body producing an egg, capable of swimming about and choosing a proper place to adhere to, where it sprouts out into branches, each crowded with innumerable distinct animals, often of complicated organization!--the branches, moreover, sometimes possessing organs capable of movement independent of the polypi." * * * * *