PENNATULA. 191 



an inch thick, constituting that part which may be compared to the quill ; 

 the other, of far larger dimensions, composed of broadened, flattened lobes, 

 to be compared to the feathered portion. Thus the Sea Pen is a very na- 

 tural name. — Plate XLIV. fig. 1. 



A slender bone, attenuated towards one extremity, and sometimes 

 hooked, occupies the centre of the smooth round portion. Therein it may 

 be indistinctly recognised through the skin, when the animal distends itself 

 with water, as this renders the parts more transparent, fig. 2. 



The size of the animal is infinitely reduced by evacuation, when it 

 appears inactive and inanimate. No one could anticipate the effect of in- 

 tumescence from its form in a contracted state. 



The whole of what we shall denominate the upper part, consists of a 

 series of lobes, diverging from either side of the middle. Ascending, they 

 commence above the smooth shank or quill, and each pair gradually en- 

 larges, until gaining the extreme breadth described as two inches, from 

 which in corresponding manner they decrease up to the summit of the pro- 

 duct. 



Several hydra? issue from the upper edge of each of the lobes, their 

 number being regulated by the dimensions of the lobes themselves, figs. 3, 4. 

 There are twenty-eight hydra? across the whole specimen represented, fig. 1, 

 that is, fourteen on each side of the rib interrupting the two leaves. This 

 hydra is precisely of the same formation as the others described in the 

 present chapter, having eight pectinate tentacula, figs. 5, 6, 7. 



The appearance of the skin of the Pennatula is very peculiar, fig. 8. 

 Numerous red shuttle-shaped spicula3 are incorporated with the surface, 

 many of them separating spontaneously and readily, fig. 9. 



The whole zoophyte is variegated white, red, and yellow, being a 

 beautiful object when displayed in full luxuriance. 



The hydra of the Pennatula, though identically of the same nature, 

 and corresponding in general description with the two preceding, rises 

 from a kind of calyx, consisting of eight flat, red pieces, which open as it 

 issues forth to expand its pectinate tentacula, and close down around it on 

 contraction. 



The position of the bone is much shifted within the shank by disten- 



