CYPRINOIDS. 149 



muscles which work the pharyngeal bones, that the teeth, whether 

 adapted for piercing or lacerating aquatic animals, or for triturating 

 vegetable substances, must be used with such force as soon to be ren- 

 dered unserviceable, and to require renewal. I had formerly made 

 sections of the dried pharyngeal bones of our common Cyprinoid 

 fishes, under this conviction, in quest of the hidden germs of the 

 replacing teeth, but without success. A subsequent acquaintance 

 with the place of development of the successors to the maxillary teeth 

 in certain fishes, as already described in the pike, alepisaur, &c., led 

 me to renew the search in the substance of the thick and soft mucous 

 membrane of the pharynx surrounding the pharyngeal bones, and 

 I soon detected the germs of the successional teeth in this situation. (1) 

 The primitive papilla first developed from the surface very soon 

 sinks into the substance of the mucous membrane, and becomes 

 inclosed by a complete capsule. I have not been able to detect in 

 the carp or tench an enamel-pulp developed from the surface of the 

 capsule covering the crown of the contained tooth : this adheres only 

 to the dentinal pulp, and by means of its base to a part of the circum- 

 ference of the capsule. The hollow cap of dentine of a half-formed tooth 

 is easily displaced from the formative pulp in consequence of its dense 

 structure presently to be described ; but the surface so exposed when 

 viewed by a strong reflected light, with a ^ inch focus, is clearly seen, 

 to be an artificial and lacerated surface : it is minutely honey-combed, 

 by the rupture of the calcified from the uncalcified portions of the 

 nascent calcigerous tubes ; and the subjacent and still unconfluent 

 cells, are seen torn from the substance of the pulp, and scattered irre- 

 gularly over its surface. When the pulp of the crown of the tooth is 

 completely calcified, the margin of its base begins to assume a liga- 

 mentous density, and attaches itself to the margin of the pharyngeal 

 bone, near the base of the tooth about to be displaced. I have not 

 observed any further stage in the singular process of transference of 

 the loosely imbedded tooth from its mucous capsule to the bone with 

 which it is destined to form a common and continuous part. 



In this process of union, which is analogous to that of the sepa- 

 rated portions of a fractured bone, the question suggests itself, by what 



(1) See PI. 57, fig 6, in which a young tooth c is exposed by a reflection of part of its 

 mucous capsule, h. 



