ENDOSKELETON. ANIMALS. 19 



angles to its longitudinal axis : they are attached laterally 

 to the internal notochordal sheath, but are separated from 

 it, above and below, by a mass of branching cells (Miiller's 

 tissue). The sheath consists of a thin elastica interna and 

 a thicker outer fibrous layer. 



The buccal cartilages, situated along the ventral and 

 lateral margins of the oral hood, are formed by the union 

 of a series of short segments. A process from the dorsal 

 end of each segment forms the cartilaginous support of a 

 cirrus. These cartilages have essential ly the same structure 

 as the notochord. 



The supports of the dorsal and ventral fins are composed 

 of a soft structureless material traversed by a few fine fibres. 

 Each support is contained within an oblong lymph-space. 



(.'horda. v. Ebner, SB. Ak. Wien, 13d. civ. 1895, p. 199. 



Buccal cartilages. Rolf, Morph. Jahrb., Bd. ii. 1870, 

 p. 101. 



Fin-supports. Pouchet, Q. J. Micr. Sci., vol. xx. 1880, 

 p. 426. 



FISHES = PISCES. 



Chemical composition. 



" Bone is a compound of animal substance and calcareous earth, 

 and serves to support the other parts of the machine, so as to 

 allow of the different parts being kept at a certain distance from 

 each other, and to be acted upon by the muscles or moving powers 

 of the body. 



"These (the Bones) are of different shapes in almost every 

 class of animals, varying as it is necessary for defence from 

 external accidents, strength, velocity, or convenient attachment 

 of muscles. 



" In some they are similar to shell, serving as a house for the 

 animal, as in the turtle ; and in the more perfect animals they 

 serve the same purpose for particular parts. 



"In quadrupeds, in some they are very cellular, thin, and 

 spongy ; in others, very hard, solid, and compact, according as 

 strength is required." Hunterian MS. Catalogue. 



A. 61. The vomer of a Cod-fish {Gadus morrhua), which has 

 been steeped in an acid, in order to remove the calcareou 



c2 



