120 Fossil Corals, — Lower Silurian RocJcs o/' Canada. 



" Buds grow from some part of the parent, generally appearing first as 

 a small protuberance upon its side, and afterwards perfecting into a complete 

 young animal with its mouth and tentacles. Each of the compound zoophytes 

 above alluded to, commenced with a single polyp and was thus formed ; bud 

 followed bud, and so the germ grew up into the coral tree or dome. Calcu- 

 lating the number of polyps that are united in a single Astra^a dcaie, twelve 

 feet in diameter, each covering a square half inch, — we find it exceeding one 

 hu^ndred thousand ; and in a Porites, of the same dimensions, in which the 

 animals are under a line in breadth, the number exceeds five and a half 

 millions ; there are here, consequently, five and a half millions of mouths 

 and stomachs to a single zooi^hyte, contril)uting together to the growth of 

 the mass, by eating, and gi^owing, and budding, and connected with one 

 another by their lateral tissues and an imperfect cellular or lacunal commu- 

 nication. There is hence ev€ry variety, as to number, among compound 

 zoophytes, down to the simple polyp, which never buds at all, and has, for 

 its corallura, a simple calicle , — it may be a tiny goblet, with a stellate cell, 

 as in the Cyathina — a cylindrical cap, as in some Dendrophyllias — or a 

 radiated disk, as in the Fungias and Cyclolites." 



After treating of the various modes of growth which result in the pro- 

 duction of trees, vases, domes, or incrusting sheets of coral, he says : " There 

 is much to surprise and interest us in tracing out the simple causes of results 

 so remarkable. The small polyp, incapable even of extending its arms with- 

 out a drop of water to inject them, is enabled, by means of a simple secretion 

 in its texture, in connexion wiih the process of budding, to rise from the 

 rock and spread wide its branches, or erect, with solid masonry, the coral 

 domes, in defiance of the waves that break over them. The microscopic 

 germ of a Gorgouia developes a polyp barely visible to the naked eye, which 

 lias the power of producing a secretion from its base. The polyp buds, and 

 finally the growing shrub is covered with branches and branchlets, many a 

 mere thread in thickness, which stand and wave unhurt in the agitated 

 waters. The same secretions fix it to its support, so strongly, that even the 

 rock comes away before the zoophyte will break from its attachment. Tens 

 of thoiLsands of polyps cover the branches, like so many flowers, spreading 

 their tinted petals in the genial sunshine, and quiet seas, but withdrawing- 

 when the clouds betoken a storm. 



" Excelsior," is the grave motto of the zoophyte. Ever upward, thry 



continue growing and elongating, although death is at work below, with as 



rapid progress. A beautiful provision protects the branchmg coral- tree — 



often the work of ages — from being destroyed by the dissolving waters, when 



exposed, on the death and removal of the polyps. Certain minute incrusting- 



corals — the Bryozoa and Sertulaiidie, together with Nallipores — make the 



surface tlieir resting place, as soon as it is laid bare, and go on spreading and 



covering the dead trunk, and so prevent the wearing action of the sea. The; 

 Madrepoi-e may thus continue to enlarge beyond its adult size ; the Caryo- 

 ph\-llia may multiply almost endlessly its cylindrical branchings, although 

 tlie living animal but tips the extremities of each : for protection is given at 

 wnce, when needed, and the polyps die, only to leave the surfajje to oih^'c 

 lurms of life, more varied and no less strange. 



