1887.] NATURAL SCIENCES OF PHILADELPHIA. 363 



it is known that in some Dipn5i, the pectoral limb is innervated 

 partly by branches from the hypoglossus and vagus, (Protopterus). 

 In the domesticated races of the Japanese Gold-fishes, popularly 

 known as "Fan-tails," in which both the anal fin and the ventral 

 lobe of the caudal fin are frequently double, it has been shown by 

 Mr. S. Watase that they arise from a pair of parallel ventral fin-folds 

 extending from the hinder part of the yolk sack to the end of the 

 notochord. He has further shown in the same memoir=J= that the 

 double, ventral series of interhajmals of the anal and caudal of these 

 fishes are the supports of the radii derived from actinotrichia and 

 the cartilaginous nodules at their bases, thus bringing these fins into 

 complete morphological harmony with the ventrals, in wdiich the 

 pelvic girdle is probably to be considered as reiDresenting modified 

 interhffimals. It indubitably follows from this, that the double or 

 paired anal and the double inferior lobe of the caudal, are to be con- 

 sidered as paired fins or limbs serially homologous with the pectoral 

 and pelvic pairs. While this embryological and morphological 

 evidence most admirably confirms the views of Dohrn as to the na- 

 ture of the paired limbs, there can be little doubt that, the double 

 anal and caudal have a just claim to bej-egarded as additional pairs 

 of limbs, making four pairs in all. Their development is further to 

 be regarded as due to reversion induced by a process of degenera- 

 tion, which has affected the whole urosome or tail of these fishes 

 from the vent backwards. This degeneration seems to be due to 

 domestication, since it is now admitted by an expert American 

 breeder of these varieties of gold-fishes, Mr. W. P. Seal, that the 

 forms most modified and prized by fanciers can only be reared in 

 restricted quarters or in aquaria or protected pools of moderate di- 

 mensions. The extreme shortening and modification of the muscu- 

 lar and axial parts of the tail, has been produced in the course of a 

 prolonged process of selective breeding, their singular changes of 

 form being probably due to disuse. The most modified forms which 

 the writer has seen alive, were slow and sluggish in their movements, 

 their enormously lengthened caudal, pectoral and ventral rays and 

 membranes seeming to interfere with any rapid motions. The short- 

 ening of the muscular portion of the tail would also aid to produce 

 such a result, as is known from Strasser's experimental researches on 

 the function of the tail in fishes. 



*0n the caudal and anal fins of Gold-fislies. Journ. Science College, Im- 

 perial University, Japan. Vol. I. 



