ON THE CAUDAL AND ANAL FINS OF GOLD-FISHES. 255 



form (Fig. 6) we observe a general agreement in the arrangement of 

 the various pieces, except in one important respect, namely, that in the 

 former case there is a double series of bones supporting the rays of 

 the ventral caudal lobe (in Fig. 7 a, h, c, d, e, f, g, pJi, a.p.li. form- 

 ing one series and a.'p'.h^ p'h^, g\ /', e', &c., forming the other) 

 corresponding to the two lateral halves, into which the tail fin is 

 divided. In the case of Fig. 6 in which all caudal rays are arranged 

 in one vertical plane, the bones supporting them form one series 

 in one plane (a, 6, c, d, e, f, g, pji., a. p.h.). 



Here I will mention that the bones supporting the caudal fin- 

 rays in a gold-fish, are each tipped by a cartilaginous cap at their 

 distal ends (Fig. 7). At the lower portion of the ventral caudal 

 lobe and close to the cartilaginous cap just mentioned there is on 

 each side a small piece of cartilage (K. Fig, 7) freely intercepted 

 between the roots of fin-rays. In our figure the left piece alone is 

 represented. 



The comparison of some individual bones in a single and a 

 double state of the caudal fin will bring out the points of difference 

 into a clearer light. 



Fig. 10 represents a penultimate vertebra from a common Caras- 

 sius in which the tail is normal. Fig. 10 a is the corresponding bone 

 taken from a gold-fish with a double tail. The neural appendage 

 and the centrum are similar in both. In the gold-fish the hœmal 

 arches, after uniting in the median line, again separate and diverge 

 in different directions (Ji.s., & Ks[). In the common Carassius how- 

 ever, the hœmal arch sends out but one process, — the hœmal spine 

 {h.s, Fig. 10). 



Fig. 11 and 11« represent the last vertebral centrum with their 

 appendages. The former is taken from the vertical and normal tail 

 of Carassius and the latter from the gold-fish with paired tail. It 



