38 



POLYPIFERA. 



jnust be the feelings excited in the mind capa- 

 ble of appreciating the result of the labours of 

 these silent agents in the economy of our 

 world ! Let us imagine for a moment the 

 stupendous scene which the mental eye may 

 view at the bottom of the ocean. Vast dis- 

 tricts of the globe spread over with a carpet 

 of this living crust, studded, as thickly as are 

 our fields with grass, with hungry flowers of 

 every various hue all actively employed in 

 carrying on the great progressive work de- 

 positing, with unobtrusive diligence, from age 

 to age, the chalky masses we have been de- 

 scribing slowly.but unremittingly, the mighty- 

 fabric grows, until at length it peers into the 

 world above the waves which nourished it, 

 and forms a land where all before was sea, 

 soon to be peopled with fit occupants, or pos- 

 sibly by the volcano's breath upheaved into 

 the clouds, to become the nucleus of a country 

 like our own, from which intelligence may 

 pour forth to irradiate the world ! 



PENNATULID^E. The Pennatulae, or Sea- 

 pens, are distinguished by Cnvier from the 

 other families of cortical polyps under the title 

 of : ' Polypiers nageurs," or swimming Poly- 

 paries, and are remarkable from the circum- 

 stance that, although they possess an internal 

 calcareous support, they are not attached 

 to foreign bodies, but seem at liberty to swim 

 about in the sea. The Pennatnlfe, properly 

 so called, several species of which are met 

 with on our o\vn shores (fig- 44), have a 



Fig. 44. 



Pennatida grisea. {After Blalncllle.) 



central stony axis, coated over its greater 

 part with a thick living cortex, the sub- 

 stance of which presents a somewhat fibrous 

 arrangement, and is capable of movements of 

 contraction sufficiently forcible to permit of 

 locomotion. The lower portion of the stem, 

 which strikingly resembles the barrel of a quill, 

 is entirely denuded of this living crust, and 

 when found in the bays upon our coast, this 

 part is generally stuck into the mud at the 



bottom like a pen into an inkstand, whilst the 

 two upper thirds of the stem are furnished on 

 each side with broad lateral appendages, com- 

 parable to the barbs of a quill, from the mar- 

 gins of which are protruded the rows of polypes 

 which minister to the support of the common 

 body of this compound animal. The lateral 

 barbs are supported by calcareous spicula de- 

 veloped in their interior and imbedded in their 

 fleshy substance, but having no other connec- 

 tion with the central stem. 



In other genera the alary appendages are 

 without any internal spines, or sometimes en- 

 tirely wanting, in which case the polypes are 

 situated upon the stem itself. 



In Renilla the body consists of a broad 

 kidney-shaped disc without any barbs, the 

 polypes in this case being distributed over one 

 surface of the disc, and in Veretillum the polype- 

 bearing part is a cylindrical finger-shaped mass. 

 The central axis in both the last-named genera 

 contains but little calcareous matter, and in 

 the whole family the individual polypes closely 

 resemble those of the Alcyonidae in their or- 

 ganisation. In Veretillum the substance of the 

 general mass is excavated into wide canals that 

 extend in the direction of the central axis 

 of the body, and terminate in wider cavities 

 within the lesser obtuse extremity. 



Many of the Pennatulidae are eminently 

 phosphorescent. 



The polypes of this group of cortical zoo- 

 phytes have eight pinnated arms, and seem to 

 be organised upon the same plan as those of 

 the Corallida?. 



AOTINIAD/E. The Actinics, or Sea-ane- 

 monies, so common on our coasts, known also 

 by the name of " fleshy polypes," are evidently 

 nearly allied to the preceding family, but in- 

 stead of secreting a calcareous polypary have 

 their bodies entirely composed of a fleshy sub- 

 stance which, in appearance at least, is not 

 very remote from muscular fibre. The ordinary 

 Actiniae are of a conical form, the base of the 

 cone forming a strong sucker, whereby they 

 attach themselves to foreign bodies, while, at 

 the opposite extremity, which is truncated, is 

 the opening of the mouth, surrounded with 

 several rows of retractile teutacula, wherewith 

 they seize their prey. They often elongate 

 their bodies, and, remaining fixed by their 

 base, they stretch from side to side as if to 

 seek for food at a distance, and when thus 

 stretched out they are very flexible and trans- 

 parent, but shrink on being irritated, and 

 contract themselves so firmly that it becomes 

 almost impossible to distinguish them from the 

 surface to which they are attached. Accord- 

 ing to some writers they can change their 

 place by gliding upon their base; or detaching 

 themselves entirely, they become swollen by 

 the imbibition of water, and thus being rendered 

 nearly of the same specific gravity as the sur- 

 rounding element are driven about in the sea 

 until they choose to fix themselves again, when, 

 by expelling the fluid from their bodies, they 

 sink again to the bottom, and settling down 

 become again fixed. It is even asserted that 

 having detached their suckers they can turn 



