9 



once found the P. Catherine, growing on the bottom of a 

 vessel in great abundance, after she bad lain at Fowey 

 harbour for a few months. The finest specimens of the 

 L. Geniculata I have ever seen, were on the dorsal and 

 caudal fins of the Picked dog-fish ( Sq. Acanthias.) These 

 and many other examples, tend to prove that these creatures 

 are of quick growth. 



The greatest number of the species of this order appear 

 to be annual; very few, apparently surviving to the second 

 year. Those growing near tide marks, cannot well be other- 

 wise, for they soon become so completely encrusted with 

 conferva? and sponges, that the apertures of many of the 

 cells are closed, and most of the others partially so, thus 

 inclosing the polype and preventing access to the water. 

 Beside this the Sea Oak and Sea Threads, the former of 

 which is frequently infested with Entomastraca, in different 

 stages of developement, grow on the fronds of sea weed, 

 which are liable to be washed off by every storm. This is 

 frequently the case, when the waves of the Atlantic roll 

 heavily and furiously in, uprooting every thing in their 

 course ; yet after a few weeks of fine weather, specimens 

 will be frequently found, even in fructification. The Sea 

 threads, so common on all our shores, are to be found in the 

 winter and spring, only in sheltered situations and beneath 

 stones, but in the summer and autumn, on most of the weeds 

 about low water mark, especially the Laminaria digitata. The 

 larger kind appear to be of a similar nature; the Sertularia 

 polyzonias, rugosa, abietina, Plvmularia falcata, frutescens, 

 cristata, &c, are more abundant about summer and autumn 

 than at any other parts of the year, though this probably 

 depends on the weather; for if the winter and spring be fine 

 they may be procured as good as at any other season. In. 

 the summer and autumn the Pinna Ingens is almost always 

 covered with different kinds of Coralline, while in autumn 

 it is commonly bare. 



As the polypidom increases in age, the horny sheath of 

 the branches and pinnae gets firmer and more condensed ; 

 and then falls off. Thus it is that in some species the 

 lower branches are always wanting; which is the case 

 with the Bottle brush Coralline, Thuiaria thvja, and less 

 so with most of the other branched species. This does not 

 depend on the violence of the waves, though that no doubt 

 effects a great deal, but is rather the result of an action 

 taking place in the animal itself. In a branch about to be 

 thrown off, the polypes first get inactive and retire to their 

 cells, the central pulps get paler, more transparent, and 

 unhealthy down as far as where the branch joins the stem; 

 at which point there is a well defined line of demarcation 



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