The development of the beautiful _Comatula rosacea_ (Fig. 41) has been described in the “Philosophical Transactions,” by Prof. Wyville Thomson and Dr. Carpenter.[33] The larva quits the egg, as shown in Fig. 42, in the form of an oval body about 1/30 inch in length, something like a barrel, surrounded by four bands or hoops of long vibratile hairs or ciliæ. There is also a tuft of still longer hairs at the narrower posterior end of the body. Gradually a number of minute calcareous spines and plates make their appearance (Fig. 43) in the body of this larva, and at length arrange themselves in a definite order, so as to form a bent calcareous club or rod with an enlarged head. [Illustration: FIG. 41.—_Comatula rosacea_ (after Forbes).] [Illustration: FIG. 42, Larva of Comatula rosacea (after Thomson). 43, Larva of _Comatula rosacea_, more advanced. 44, Larva of Comatula rosacea, in the Pentacrinus state.] As this process continues, the little creature gradually loses its power of swimming, and, sinking to the bottom, looses the bands of ciliæ, and attaches itself by its base to some stone or other solid substance, the knob of the club being free. The calcareous framework increases in size, and the expanded head forms itself into a cup, round which from five to fifteen delicate tentacles, as shown in Fig. 44, make their appearance. In this stage the young animal resembles one of the stalked Crinoids, a family of Echinoderms very abundant in earlier geological periods, but which has almost disappeared, being, as we see, now represented by the young states of existing more advanced, free, species. This attached, plant-like condition of _Comatula_ was indeed at first supposed to be a mature form, and was named Pentacrinus; but we now know that it is only a stage in the development of _Comatula_. The so-called Pentacrinus increases considerably in size, and after various gradual changes, which time does not now permit me to describe, quits the stalk, and becomes a free _Comatula_. The metamorphoses of the Starfishes are also very remarkable. Sars discovered, in the year 1835, a curious little creature about an inch in length, which he named _Bipinnaria asterigera_ (Figs. 45-47), and which he then supposed to be allied to the ciliograde Medusæ. Subsequent observations, however, made in 1844, suggested to him that it was the larva of a Starfish, and in 1847 MM. Koren and Danielssen satisfied themselves that this was the case. Figs. 45 and 46 represent the front and side view of a Bipinnaria found by Müller[34] near Marseilles. _a_ is the mouth, _b_ the œsophagus, _c_ the stomach, _c_´ the intestine. Fig. 47 represents a somewhat older specimen, in which the Starfish (_k_) is already beginning to make its appearance.