4-24 Report of the State Geologist. 



" But differences of this nature can not be formed by the sim- 

 ple juxtaposition of new calcareous layers under those primi- 

 tively formed, for the soft parts of the animal — the only ones 

 which can be the seat of a secretion of this calcareous matter — 

 do not extend over the surface which is thus modified, and the 

 position of the cells thus immersed in the apparently common 

 mass of the polypidom is often such that we can not attribute 

 their change of form to any operation or friction of foreign 

 bodies. 



"It appears evident to us that these facts indicate the presence 

 of life in the substance which composes the parietes of these 

 cells and can only be explained by the existence of a nutritive 

 movement, like to that which in the configuration of bones effects 

 analogous modifications. 



" To know better the. nature of these cells, I submitted to the 

 action of nitric acid diluted with water a part of a polypidom 

 recently taken from the sea. A brisk effervescence was visible 

 immediately, and in some minutes the cells became flexible and 

 separated from one another. Before treating them thus no dis- 

 tinct membrane was seen on the internal wall of these cells, and 

 when the nitric acid had destroyed all the calcareous carbonate 

 on which their rigidity depended these same parietes still existed 

 and had not changed their form much, only they were formed 

 now of a soft and thick membrane constituting a bag,* in the 

 interior of which we perceived the digestive apparatus of the 

 polype. The opening of this bag was no longer truncated, as it 

 appeared when the texture of the membrane was thickened by 

 the stony deposit from which we had just freed it, but the 

 membrane was continued uninterruptedly with the tentacular 

 sheath. 



" We see, then, that in the Eschares, the cell in which it is said 

 the polyp retires as into a shell, is a component part of the 

 animal itself, in which it conceals itself, if we may use the com- 

 parison, as the hedgehog enters into the thorny skin of his back. 

 It is not a calcareous crust which is molded on the surface of its 

 body, but a portion of the general tegumental membrane of the 

 skin of the polyp, which by a molecular deposit of earthy mat- 

 ter in the meshes of its tissue, ossifies as the cartilages of superior 

 animals ossify, without ceasing to be the seat of a nutritive 

 movement. 



