SECT. IT. PENNATULID&. 129 



and these combine in bundles at the base of the cells, in 

 which the polypes live. The back of the pen, lying 

 between the feathery wings, is sometimes smooth, some- 

 times crowded with scales, arising from the development 

 of the spicules with which it is filled. The eggs of this 

 animal are yellow, and have the size and form of poppy 

 seeds. They are developed into ciliated larvae within- 

 the polypes, which come out at their mouths, and swim 

 away ; but their activity is much diminished when they 

 have acquired their mature form. These Pennatulse in- 

 crease also by a kind of budding. There are species of 

 phosphorescent sea-pens in all the European seas and 

 Indian Ocean. 



The Virgularise are sea-pens which have long slender 

 stems, with short transverse pinnules, on both sides of 

 their extremity : they have no spicules, and are remark- 

 able for the contractile power both of their axis and 

 polypes. Mr. Darwin mentions a species he met with 

 during his voyage in the Southern Ocean, which seems to 

 be akin to the Yirgularia juncea common in the Indian 

 Seas. They were long and slender, projecting in vast 

 numbers like si ubble above the surface of muddy sand. 

 TVlien touched or pulled, they suddenly shrunk down 

 with such force as to disappear partly or altogether. 

 Sensitive as these animals are, they have no nerves ; 

 hence their motions must be owing to the irritable 

 nature of muscular fibre. The eggs of the Yirgularia 

 mirabilis, native on the Scotch and Norwegian coasts, 

 are formed in the fleshy coat at the base of each polype. 

 As soon as they acquire their yellow colour and ciliated 

 surface they enter into its body, and revolve in it for a 

 little time before they come out at its mouth. 



The family of the Tubipora, inhabitants of warm seas, 

 are the most beautiful of the Alcyons. They consist of 

 rounded masses of considerable size, formed of fragile, 

 hollow, and nearly parallel calcareous tubes. The tubes 



VOL. II. K 



