1893.] NATURAL SCIENCES OF PHILADELPHIA. 85* 



was developed, so far at least as to duplicate the hypural system of 

 bones of the tail, and consequently the tail itself, while this doubling 

 would also manifest itself farther forward so as to sometimes double 

 the anal fins as well. The caudal part of the notochordal axis is 

 rarely doubled, though there is an evident tendency to do so in some 

 individuals. 



The great exaggeration in the development of the fins in Japanese 

 Gold-fishes, especially the caudal, is, however, not wholly accounted 

 for by the theory of the inheritance of tendencies toward monstrous 

 development. Nor is the obvious degeneration of certain parts of the 

 muscular system in some of the races thus accounted for. Nor can 

 we again account for the differences in the relative lengths of the 

 intestine in the different races on such a hypothesis. Only one 

 structure, the squamation and the number of myotomes, seems to 

 have remained constant in the course of the great modifications 

 which these fishes have undergone. I find that the number of rows 

 of scales in the lateral line in all the races I have studied, presents 

 practically no variation ; that is, the number of scales in the lateral 

 line varies only from 25 to 26. The number of myotomes is 

 also constant in all the races, and corresponds to the number of 

 transverse rows of scales. In order to make the facts stated above 

 somewhat more easy of apprehension, I have tabulated the result of 

 a series of careful measurements, based upon three races, viz: (1) 

 the normal or common gold-fish, Carassius auratus ; (2) a long- 

 bodied double-tailed variety of great beauty, which has been reared 

 in the aquaria of Dr. W. H. Wahl, who has kindly let me have 

 some dead individuals, for study ; (3) a short-bodied double- 

 tailed race with a very protuberant abdomen, which were imported 

 from Japan, and of which dead examples were furnished me by 

 Mr. W. P. Seal. 



I found that the head in all cases was the least variable part of 

 the animal. I have accordingly regarded it as a standard of com- 

 parison in a general final table. The following tables will explain 

 themselves, and give absolute measurements in millimetres of the 

 same parts of the three races in parallel columns. 



By urosome is meant the part of the trunk behind the body cav- 

 ity, and between the latter and the base of the caudal fin. I have 

 compared the musculature of the abdomen and urosome to a frus- 

 tum of a cone with an elliptical cross section. In this way it is 

 possible to show, taking the absolute measurements in connection 



