34 THE VOYAGE OF H.M.S. CHALLENGER. 



Ovum of a Scomhresocid (PL V. fig. E). 



The surface-net enclosed in the Atlantic on February 29, 1876, a single ovum, 

 2 '5 mm. in diameter, which by the development on its surface of long filaments proves 

 to be that of a member of the family of Scombresocidfe. The embryo is considerably 

 advanced in development, its outlines being clearly visible. The ovum differs from that 

 of Belone and Scombresox in having shorter and fewer filaments ; also the filaments 

 have no swelling at the base. It may be that of an Exocoetus, the ovum of which I 

 believe is stDI unknown. 



The ovum, which was mounted in glycerine for the microscope immediately after 

 capture, gives the impression of a regular arrangement of the filaments in four concentric 

 circles on each hemisphere, and with a single filament at each pole. 



Hemirhavqihus sp., young. 



One specimen only can be referred with certainty to this genus, but it is not 

 sufficiently advanced in growth to determine the species. It is 1|- inches long, and was 

 captured on the passage from Tenerife to St. Thomas in the West Indies. The lower 

 jaw projects y\ of an inch beyond the upper, the latter being short and broad as in the 

 mature fish ; no teeth whatever can be distinguished in this specimen. 



Scombresox, j^oung. 



The fry and young of this genus belong to the most common forms of pelagic Ufe, 

 and numerous specimens up to If inches in length were captured by the tow-net. Those 

 from the Atlantic I have referred to Scombresox saurus, and those from the Pacific to 

 Scombresox forsteri, without being able to discover in these immature specimens the 

 slight differences by which those closely allied species are distinguished. Of the dates of 

 capture of the Atlantic specimens were noted March 7, April 28, and May 7 (1876) ; the 

 Pacific specimens are from 1 to If inches long, and were captured on various occasions 

 in the month of July, 187.5. 



Belone sp., young. 



Among the numerous pelagic young Scombresocidse collected by the Challenger, or 

 obtained from other sources, there is only one which I can refer without hesitation to 

 Belone. It was caught in September about forty miles north of Demerara, and is 

 21 mm. long. It cannot be determined specifically. The body is subcylindrical in shape 

 with a rather elongate caudal fin. Both jaws are prolonged and toothed, but the length 



