1893.] NATURAL SCIENCES OF PHILADELPHIA. 91 



family, or defensive organs, such as the horns of the ox and ante- 

 lope families, which are produced at a relatively late period. 



The fact that the very long fins of the full grown individuals of 

 the double-tailed races of Gold-carp are only fully developed at a 

 very late period of the growth of the animal, is in harmony with the 

 view that the hypertrophy of those organs is associated with a 

 correlative degeneration of the muscular system of the trunk, and 

 a possible use of these structures with their great amount of surface 

 as respiratory organs, in the restricted and badly aerated tanks 

 and aquaria in which they have been bred for centuries. 



Since the above was written, Mr. W. P. Seal has sent me a series 

 •of the " telescope-eyed " double-tailed race of Gold-carp. This, 

 together with the materials previously supplied by the same gentle- 

 man and Dr. Wahl, enables me to greatly extend my comparisons 

 and also, as will be seen below, to add some very remarkable facts to 

 •our knowledge of these singular domesticated races of fishes as com- 

 pared with their wild congeners, long since introduced into the 

 Schuylkill, and now native to that river. 



The most astonishing peculiarity of the " telescope-eyed " race is 

 the development of the eyes. The latter are very much larger pro- 

 portionally than in the common or in any other races, so that the 

 eyes actually protrude from the orbits in a most grotesque manner. 

 The size of the eyes on opposite sides of the head even seem to vary 

 somewhat, and in the extent to which they protrude from the 

 orbit. In some specimens the eye-balls are a third more in diam- 

 eter across the equator than in either the common or the other 

 double-tailed races. A broad band or ring of integument passes 

 all round the equator of the eye-ball joining the cornea distally 

 and the margin of the orbit proximally. 



The most surprising fact of all, however, is the shape of the eye- 

 ball in the telescope-eyed race, in that the eye-ball tends to become 

 greatly elongated in the direction of its optic axis. Sometimes the 

 difference between the axial and equatorial diameter is as much as 

 three millimetres, constituting an extremely myopic form of eye-ball. 

 The form of the eyeball in the common race is flat or hypermetropic 

 in character. A gradual passage from the hypermetropic form of 

 eye-ball to the myopic is shown in the following table, as based 

 upon actual approximate measurements of the eye-balls of indi- 

 viduals of the three races. 



