FLUSTRA. 3 



speedily when withdrawn from their native abode. Hence, in studying 

 their history, they demand unremitting care. All this may result from the 

 delicacy concomitant on the foliaceous structure of the product, for the 

 leaf of some is as thin as paper. The higher organization of the animal may 

 render it more susceptible of injury, or life itself, subsisting under such 

 peculiar conditions, may be virtually of shorter duration. Liable to recur- 

 ring embarrassments, therefore, a series of connected observations on the 

 origin, the increment, permanence and decay of the Flustra, as the genus 

 is denominated, together with the mode of perpetuation, — its perfect 

 history scarcely comes within the scope of those opportunities which indi- 

 vidual naturalists may hope to enjoy. 



The earlier authors having failed to select the characteristics suf- 

 ficiently prominent for distinguishing such products as should be compre- 

 hended within certain limits, circumscribing the genus Flustra, has allowed 

 the gradual accumulation of a very miscellaneous assemblage. 



I shall not adventure on any critical correction, but confine my re- 

 marks, in the first place, to those species which are strictly foliaceous, 

 that is, composed of leaves penetrated by cells on one or on both surfaces, 

 and occupied by living hydroe. 



§ 1. Flustra carbasea — The Laivn Sea Mat. — Plates I. II. — This 

 is a thin foliaceous product, which may be considered perhaps as only a 

 single subdividing leaf, constituting the subordinate parts. It rises by a 

 short flattened stem, diverging to both sides in somewhat dichotomous for- 

 mation, not dissimilar to the cleaving of the Sertularice, formerly described. 

 The portions of the leaf are separated by curvatures, not by angles, and 

 the outlines of the whole edge are also larger or smaller curvatures 

 throughout. But great irregularities prevail, among a number of speci- 

 mens, in the partition and proportion of the parts. Its common form ex- 

 hibits few divisions, or little subordinate organization. When the leaf is 

 entire, the edge is deeply waved : and sometimes, though rarely, it con- 

 sists of a long plain arc, instead of several different curvatures. 



The finest specimens are towards three inches in height, and diverge 



