262 



s. WATASE 



conlescence of the same folds. 



The occurrence of double preanal folds in gold-fishes coincident 

 with the double post-anal folds, harmonizes with my view. The 

 median preanal and post-anal folds usually met with in a normal 

 Teleost are then both to be looked upon as the coalesced state of 

 the two folds. 



The dorsal fin has also been interpreted by some authors to have 

 arisen througb coalescence of two dorsal folds (Parapodia). As the 

 probable cause of this coalescence, is assigned the closing of the 

 medullary plate. In tliis connection it ought to be mentioned that 

 in gold-fishes the dorsal fin and that portion of the caudal lying 

 dorsal to the vertebral axis are never met with in a double state, — • 

 showing that the median unpaired condition of the dorsal fold is 

 more strongly rooted than in the ventral fold. 



Provided that the pectoral and the ventral fins are really speciali- 

 zations of the same lateral folds as the post-anal fins, all these are to 

 be regarded as homologous. The interhœmals might then be looked 

 upon as representatives of the pelvic or shoulder girdles. The 

 homology of the anal fin with the more anteriorly situated limbs is 

 most apparently borne out in the case where it is paired as was 

 described on page 258. The paired caudal fin, accompanying the 

 most complicated portion of the axial skeleton, has undergone such 

 modifications that the recognition of all parts homologous with those 

 of the more anteriorly situated appendages has become a difficult 

 task. The analogy of position however disposes me to assume 

 that the free cartilaginous nodule (Fig. 7. K.), intercepted between 

 the diverged extremities of caudal fin-rays, represents either some 

 degenerated Interhœmals or some bony nodules similar to those 

 found in the anal fin (Figs 17 & LS, n, ?/, ), or perhaps the aggregate 

 of both. 



