sre so tenacious of liff, as to I)e inc.apahle cf destrnclion 

 by mutilation. "When a heail is severed from a body, the 

 latter acquires a new head, and the head a new hod v. The 

 bead, or even the ^%hole body, of one may be tjrafted on 

 the body of another; or they may be divided into a multitude 

 of |>arts a'ld each will become a new body and a perfect 

 animal. Tiiey may even be turned inside out, or slit up and 

 extended as a membrane, without much apparent injury. 



Per damna, per caedes, ab ipso 

 Ducit opes animnmijne ferro. 



When tlipse experiments were first made pnblic, they ex- 

 ril(>d, as they well nii2;ht, the wonder of the world, nor do 

 tliev' now cease to astonish us, thou<»;h made familiar by 

 f)n<lina: a place in most elementary works on Natiiral History 

 and Natural Theolosiy. Thnu2;h the polypes of the sheathed 

 or horny genera are incapable of under<^oing such remark- 

 able clians^es, yet the same disposition pervades the whole 

 order. If for instance, the Sea Oak (Sertularia pumila) or 

 the Great-tooth Coralline (S. polyzoniiis) be allowed to 

 remain in impiire water for a few days, their hearls and ten- 

 lacula will frrfjuently drop ofl" and the polypes shrink into the 

 cells ; but, afterwards if the water be frequently renewed, a 

 new head and tentacula will soon be formed. At first the 

 new parts dificr in colour from the older portions, but this 

 diflference in a very short time is entirely lost, although the 

 new tentp.crda are rarely equal in number to the old ones : 

 a circumstance that explains the variety assigned by difl'erent 

 authors to the same species. In the Laomedea geniculata, for 

 instance, I have counted in dillVrent specimens, 11, 19, 20 up 

 to 29 tentactda, so that no reliance can be placed on them in 

 determining the species. 



In their actions, these animals are comparatively sluggish; 

 and in strucnire present, perhaps, the lovvest form of 

 organized animal existence. When examined under a mi- 

 crt)scope, not a single fibre is discovered by which their 

 various actions can be supposed to be performed ; but 

 they appear to be composed entirely of minute distinct gran- 

 nies, each of which seems to possess a power of independent 

 vitality. The impressions which produce the motions of 

 the tentacula and body appear to be communicated from 

 granule to granule chiefly t)y contact. The animal seems to 

 be a sitriple granular pulp; into which a central depression 

 is fortned, which performs the oihce of a stomach, the nutri- 

 ment being conveyed through the mass by iudjibition, and the 

 refuse or excrenientary part ejected throtigh the same orifice 

 by which it is taken in. That the nutriment is conveyed by 

 imbibition aj'pears fiom the fact, that the colour of the 



