8 



T liave some reason to believe that a large specimen can be 

 formed under favorable circumstances, in the course of 

 fourteen days. In the smaller species, a transient cessation 

 of growth takes place at the various septa ; at these points 

 the ptilp gets enlarged, and in the Sea Oak, S. pnmila, where 

 the two cells and stem are formed simultaneously, it appears 

 as one very great enlargement, At first this enlargement 

 of tlie pulp is undistinguished by parts or markings, which 

 is however but of short duration, for three dark points 

 appear on the pulp indicating the situations of the central 

 pith with a polype on either side. The concentration or 

 organization proceeds from below upwards, and the dark 

 spots become more and more defined and separated from 

 each other, the formation of the polype and cell being as 

 described above. The extremities of the pinna? and trunk 

 are closed during growth, and not open, as some authorities 

 have stated.* The growth certainly takes place rapidly, and 

 chiefly about summer and autumn. In a specimen of the 

 Sertularia argentea, now before me, a slioot of six inches 

 has taken place, which is of a pure silvery white, while the 

 lower and ohier portion is of a light brown colour. On a 

 cross section of the stem of the new part, the horny sheath 

 was found to be of equal consistence throughout, and very 

 delicately spongy or cellular; in a cross section of the older 

 stem the texture was not so elastically spongy, but harder 

 and firmer, more especiall}- towanls the inner circumference 

 of the ring, wliere there was a brown zone occupying nearly 

 one half the diameter, as if a solid material had been de- 

 posited in the intercellular substance, or the cells had been 

 more closely pressed together. As another instance out of 

 many, of the rapidity of growth in these creatures, in a spe- 

 cimen of the compound variety of the great tooth Coralline, 

 ( S. ■polyzonias) about eight inches high, an egg of the 

 Rough Hound, (Sqvalus caniaila) has been deposited, and by 

 its tendrils has twined round the branches and bound them 

 into one large clump; through the folds however fresh 

 shoots have sprung out in such great abundance as completely 

 to hide the ovum from sight, unless the branches are first 

 turned aside. On examining the ovum no advancement in 

 developement had taken place; the cicalricnia having the 

 same appearance as those taken from the animal. From 

 this specinien being taken at the time at which the fish were 

 depo^iting their ova, it is probable, that it had not long been 

 shed. In another instance, several very good specimens of the 

 same Coralline mixed with Pinmidaria cristata and P.falcata 

 were growing on the case, but its contents had escaped. I 



* Jones' Outline of the Animal Kingdom, p. 47. Grant, &c. 



