2 



are so tenacious of life, as to be incapable of destruction 

 by mutilation. When a bead is severed from a body, the 

 latter acquires a new head, and the head a new body. The 

 head, or even the whole body, of one may be grafted on 

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

 of parts and each will become a new body and a perfect 

 animal. They 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 animumque ferro. 



When these experiments were first made public, they ex- 

 cited, as they well might, the wonder of the world, nor do 

 they now cease to astonish us, though made familiar by 

 findins; a place in most elementary works on Natural History 

 and Natural Theology. Though the polypes of the sheathed 

 or horny genera are incapable of undergoing such remark- 

 able changes, yet the same disposition pervades the whole 

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

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

 remain in impure water for a few days, their heads and ten- 

 tacula will frequently drop off 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 differ in colour from the older portions, but this 

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

 new tentacula are rarely equal in number to the old ones : 

 a circumstance that explains the variety assigned by different 

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

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

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

 determining the species. 



In their actions, these animals are comparatively sluggish; 

 and in structure present, perhaps, the lowest form of 

 organized animal existence. When examined under a mi- 

 croscope, 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- 

 ules, 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 by contact. The animal seems to 

 be a simple granular pulp; into which a central depression 

 is formed, which performs the office of a stomach, the nutri- 

 ment being conveyed through the mass by imbibition, and the 

 refuse or excrementary part ejected through the same orifice 

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

 imbibition appears from the fact, that the colour of the 



