78 



QUEKETT'S LECTURES ON HISTOLOGY. 



digestive sacs, or polypes, to maintain its integrity. If a vertical section 

 be made of any Coralline, such for example as the C. officinalis, fig. 85, a, 

 we shall find that, on examination with the lowest powers, it will exhibit 

 two kinds of structure, both of which are essentially cellular — that on the 

 exterior being composed of small cells of hexagonal figure, whilst in the 

 interior they are more elongated, and generally of a brownish colour ; this 

 is especially the case if a section should inchide a joint. In the fresh 

 state the contents of the cells can be easily made out, and the central ones 

 are not unfrequently full of greenish granules like Chloro]>hylle. The 

 lime is not in the interior of the cells, but appears to be on the outside of 

 the cell-walls, which are rendered opaque and thick in consequence. A 

 portion of the vertical section, as seen under a power of 200 diameters, is 

 represented at c : the dark parts on the outside of the cells there shown are 

 the calcareous material ; the cells in the centre, as before noticed, are of 

 an elongated figure, having little or no lime about them ; these also are 

 exhibited at c, but the loose cells on the right side of the lower part of the 

 figure, formed part of the articulation, and are entirely destitute of lime. 

 A transverse section of one of the joints of the same Coralline, as shown at 

 h, is wholly made up of cells, those on the margin being rather larger 

 than the central ones ; both have an abundance of lime around them, as 

 represented under a power of 200 diameters at d. The cells seen upon the 

 upper portion of this figure having been deprived of their lime, are in 

 consequence rendered very apparent. All the Corallines exhibit nearly 

 the same structure, the outer portions being composed of cells of hexagonal 

 figure, and the central of elongated ones ; the former are always coated 

 with lime, whilst the latter are only partially so, and it is by the absence 

 of the lime from these cells, at particular points, that the articulations are 

 formed. 



Fig. 8r>. 



a, a vertical section of a joint of Corallina officinalis magnified 50 (iiameters. 6, a transverse 

 section of the same, c, a portion of the vertical section magnifled 200 diameters, d, a portion 

 of the transverse section magnified 200 diameters. 



