G. GENERAL NATURAL HISTORY AND ZOOLOGY. 323 



forward into the cavity of the mouth, where they remain 

 closely packed, heads forward, the cheeks of the parents 

 swelling out as the young increase in size, and presenting a 

 most singular appearance. A few of the young sometimes 

 remain between the branchial plates, but most of them pass 

 forward as stated. M. Lortet did not ascertain at what pe- 

 riod the young left the mouth of the parent, but presumed 

 that they remained there a considerable time. Whether, 

 after they once leave, they re-enter for protection, is not 

 stated. It is very remarkable that the young are not swal- 

 lowed by the parent while in their receptacle. 6 i?, Decem- 

 ber 13, 1875. 



CAUSE OF THE BLACK SPOTS ON THE SCALES OF FISH. 



The abnormal occurrence of black spots or specks upon 

 the scales or external surface of fishes has frequently been 

 observed, and quite often mistaken for regular coloration. 

 Dr. Fatio, of Geneva, however, has been investigating some 

 of these cases, and finds that in nearly all of them a small 

 parasitic worm occupies the centre of this spot, and is easily 

 observable by the microscope. This is inclosed in two cysts, 

 with a peculiar liquid between, the inner being oval and 

 transparent, and the outer round, with thick fibrous walls, 

 outside of which is the mass of star-shaped pigment cells. 

 The further stages of this worm have not yet been worked 

 out, although it is quite probable that when the fish is de- 

 voured by its predaceous neighbors, this enters into another 

 staixe of the alternations of veneration which have become 

 so familiar of late years to investigators.^18 yl, il/arcA 19, 

 IBYS, 10. 



REMARKABLE STRUCTURE OF YOUNG FISHES. 



Dr. Gunther, of London, has recently discovered that the 

 young of the sword-fishes and chsetodons possess structures 

 exceedingly different from that of the adults. In the young 

 choetodons the front of the body is shielded with large bony 

 plates, which in one species are produced into three long 

 equidistant horns, w^hich diverge ray-like from the body. In 

 the sword-fishes the scapular arch is prolonged into a horn 

 at the lower part, and the belly fins are wanting. There is 

 no sword, but the jaws are long, of equal length, and both 



