Fig. 40, Larva of Echinus, ✕ 100. A, front arm; F, arms of the mouth process; B, posterior side arm; E1, accessory arm of the mouth process; a, mouth; a´, œsophagus; b, stomach; b´, intestine; o, posterior orifice; d, ciliated bands; f, ciliated epaulets; c, disc of future Echinus (after Müller).
Fig. [40] represents a larva, probably of another sea-egg (Echinus lividus), from the Mediterranean, and shows the commencement of the sea-egg within the body of the larva. The capital letters denote the different arms: a is the mouth, a´ the œsophagus, b the stomach, b´ the intestine, f the ciliated lobes or epaulets, c the young sea-egg.
Fig. 41.—Comatula rosacea (after Forbes).
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 orops 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.
Fig. 42, Larva of Comatula rosacea (after Thomson). 43, Larva of Comatula rosacea, more advanced. 44, Larva of Comatula rosacea, in the Pentacrinus state.