132 



MUSCULAR SYSTEM, 



FIG. 62. 



most irritable and contractile parts of the body in all zoo- 

 phytes, and the most exquisitely sensitive to external im- 

 pressions. The polypi are prehensile sacs or mouths deve- 

 loped from and continuous with the fleshy substance of 

 zoophytes, their margin is surrounded with delicate fleshy 

 arms or tentacula, which vary in different species from six 

 to more than thirty. The polypi are seen extended from 

 the fleshy substance of the isis in Fig. 62. A., d, d, the 

 fleshy part covers the branch at (c,) and is removed 

 from the jointed skeleton at (0, a, b, b.) The fleshy part of 

 the isis appears to be incapable of bending the joints of the 

 skeleton, and it has as little effect on the skeleton in the 

 other corticiferous zoophytes. Where it forms thin laminae 

 consolidated with calcareous matter, and disposed around 

 the parietes of cells, as flustrce, eschara, and cellarice, it 

 is as little capable of moving the axis. In the cellaria 

 loriculata (Fig. 62. C,) where the cells of the polypi (a, a,) 

 are disposed in regular consecutive pairs with their apertures 

 opposite, and with contracted articulations (c, c,) at the 

 bases of the cells, neither the enclosed polypi, nor the 

 fleshy part of the entire animal are capable of bending the 

 articulations. The slow contraction of the pennatula phos- 

 phorca coils up the thin flexible extremities of its calcareous 



