290 Dr. Hancock on the Composition 'of the Fin Rays 



perfect their pliancy, they are subdivided into several branches, 

 fore and aft, not laterally ; and each branchlet, however minute, 

 jnay be observed, with a lens, to be composed precisely as just 

 noticed of the larger stems. Their jointed and channeled 

 structure reminds one of the culm or stem of a rush when 

 split open *. 



This wonderful organization is, more or less, observable in 

 the fin rays of all the bony fishes, — it is in general most notable 

 in the tail fin, which may be considered as the main-spring 

 in propelling the animal forward in opposition to the watery 

 medium ; the pectoral and ventral conduce to the same end, 

 as well as facilitating various other evolutions in the water, — 

 whilst the anal serves, in the manner of a rudder, to steer or 

 direct its motion through the element. The lateral action being 

 particularly required in this fin, we find it generally to consist 

 of the soft pliant structure ; whilst those of the back, the office 

 of which is less apparent, are more frequently composed of 

 the rigid kind, or firm entire spinose rays, which possess a 

 much less perfect side motion. It is plain, however, when we 

 consider of it, that this fin (the dorsal) serves to give a steady 

 motion ; it may usually be observed elevated when the fish 

 is swimming with any velocity, and contributes to maintain its 

 position in the water, or to prevent its falling on either side. 



In many individuals of the goldfish {cyprinusauratus), which , 

 for the splendour of its colours, is kept in glass jars, we observe 

 the lower half of the caudal fin to be double, so that the tail 

 appears trifid ; — this, perhaps, ma%be regarded as one of those 

 curious anomalies resulting from transmigration (being indige- 

 nous to Japan). The bones composing the rays being, as in 



* Linnaeus in his Syst. Nat., torn, i., p. 1127, Lipsise, 1788 — Pisces — observes, 

 " Spina a radiis geminis coadunatis ortae, nee ut muticae radiis dichotomis." This is 

 a very singular error of that great naturalist ; and it has probably given rise to a simi- 

 lar remark, which I observe m the Regne Animal of M. Cuvier, vol. ii. p. 123 of the 

 new edition, where he observes, that " the rays are of two kinds : one consisting 

 of a single bony piece, commonly hard and pointed, somewhat flexible and elastic, 

 divided longitudinally — ^these are called spinose rays ; the others are composed of a 

 great number of small articulations, and are usually branched at their extremities : 

 these are called soft rays, articidated or branchy (branchus ?)" Now the spinous 

 rays never rise in twins joined together (gemims coadunatis), as asserted by Lin- 

 naeus, or as stated by Cuvier, divisee longitudinalement, — nor ever separated at either 

 extremity, or in any manner whatever. We see by tliis, however, that naturalists 

 have entertained some idea, though a very confused and erroneous one, regarding 

 the non integral structure of certain radii in the fins of fishes. A similar statement 

 occurs in some of the older writers. It may, therefore, be considered, perhaps, as 

 **uccessively copied by different authors from those of a more remote antiquity. 



