50 ANGLING. 



throughout the whole of their frame work, in their 

 branchiae (the external border of which is fixed to 

 the skin, and through which the water is allowed 

 to escape only by narrow openings), and in other 

 important parts of their organization, distinctive 

 characters which obviously separate them from all 

 other fishes. They are in fact destitute of true 

 bones, their harder parts consisting only of a homo- 

 geneous and semitransparent cartilage, which is 

 merely Covered on the surface in certain genera by 

 a layer of small, opaque, calcareous granules, closely 

 set together. In the Lampreys even this envelope 

 is wanting, while among the Ammoccetes the skele- 

 ton continues in an actually membranous condition. 

 The sturgeons and chimerae partake in some manner 

 of the lamprey character in relation to the softness 

 of their spines, but the first named genus is 

 possessed of many true bones of the head and 

 shoulder. 



Other fishes differ in their osteological character 

 chiefly in the hardness of their skeleton, and it is 

 without reason that the fibro-cartilaginous kinds 

 have been associated by some authors with the 

 Chondropterygii. The calcareous matter, that is, 

 the phosphate of lime, is deposited in layers and 

 fibres in the cartilage which forms the basis of their 

 bones, precisely in the same manner as among the 

 hard-boned species, but less abundantly ; and the 

 texture of the bone never becomes so hard and 

 homogeneous as among the osseous kinds. Thus 



O O 



in Tetradon mola we perceive, as it were, only scat- 

 tered fibres amid the membranes, and in Lophius 



