44 James D. Dana, Esq., on the Structure^ 



pores, Serpiilas, and some molluscs. In many instances the 

 lichen-like Nullipore grows at the same rate with the rate of 

 death in the zoophyte, and keeps itself up to the very limit of 

 the living part. The dead trunk of the forest becomes covered 

 with lichens and fungi, or in tropical climes, with other foliage 

 and various foreign flowers : so among the coral productions 

 of the sea there are forms of life which replace the dying 

 polyp. The process of wear is thus entirely prevented. 



The older polyps, before death, often increase their coral 

 secretions within, filling the pores occupied by the tissues, 

 and rendering the corallum more solid ; and this is another 

 means by which the trees of coral growth, though of slender 

 form, are increased in strength and endurance. 



The facility with which polyps repair a wound, aids in 

 carrying forward the results above described. The breaking 

 of a branch is no serious injury to a zoophyte. There is often 

 some degree of sensibility apparent throughout a clump, even 

 when of considerable size, and the shock, therefore, may oc- 

 casion the polyps to close. But in an hour, or perhaps much 

 less time, their tentacles will have again expanded ; and such 

 as were torn by the fracture will be in the process of com- 

 plete restoration to their former size and powers. The frag- 

 ment broken off, dropping in a favourable place, would become 

 the germ of another coral plant, its base cementing by means 

 of coral secretions to the rock on which it might rest ; or if 

 still in contact with any part of the parent tree, it would be 

 reunited and continue to grow as before. The coral zoophyte 

 may be levelled by transported masses swept over by the 

 waves ; yet, like the trodden sod, it sprouts again, and continues 

 to grow and flourish as before. The sod, however, has roots 

 which are still unhurt ; while the zoophyte, which may be 

 dead at base, has a root — a source or centre of life— in every 

 polyp that blossoms over its surface. Each animal might 

 live and grow if separated from the rest, and would ultimately 

 produce a mature zoophyte. 



We close this review of the characters of coral animals, 

 which is a mere abstract of the fuller descriptions in the 

 General Report on Zoophytes, by alluding briefly to a second 



