The Origin of the Electric Organs in Astroscopus Guttatus. 



149 



aiSi^fi 



between the electric tissue and the eye-muscle tissue is evident, 

 although the rectus inferior muscle has become so narrow as to appear as 

 a mere thread and the rectus superior muscle is split into several parts 

 by the passage of the electric nerve through it. The organ is bounded 

 by the upper part of the muscle adductor mandibulse, the muscle 

 levator arcus palatini, and the anterior and posterior divisions of the 

 muscle adductor arcus palatini. 



The authors supposed the organs to 

 have been derived from one of the 

 bounding muscles, probably the muscle 

 levator arcus palatini, since this has a 

 more intimate connection with the organ 

 than either of the other two, but the 

 possibility was suggested of the tissue 

 having arisen from the eye-muscles which 

 pass through the organ. It was impos- 

 sible to follow up either of these theories, 

 however, without embryonic material, 

 and a search for embryos was at once 

 begun. 



Opsanus and Porichthys lay their eggs 

 in nests or easily available places. This 

 did not prove true of Astroscopus, how- 

 ever, and Professor Dahlgren studied the 

 habits of the fish to find if possible where 

 to look for the young forms. He found 

 the habits of Astroscopus to be essentially 

 similar to those of an allied form, Urano- 

 scopus scaber, a native of the Bay of 

 Naples. This fish, as explained by Dr. 

 Cerruti (so), lays a pelagic egg which 

 at once floats from the bottom, where it 

 is deposited, to the surface, where it 

 rapidly forms an embryo that lives on the surface for many weeks 

 and months. Astroscopus has a large pelagic egg which is laid in May 

 or June and develops into a larva very rapidly. It lives on the surface 

 50 to 60 miles from shore and gradually works inshore as it approaches 

 adult Ufe. Toward the latter part of the summer the young fish, over 

 an inch in length, moves from the surface to the bottom and seeks the 

 sand, in which it burrows and spends the greater part of its hfe. With 

 this information extensive towing work was undertaken, and through 

 the kindness of Dr. Henry B. Bigelow, of the Museum of Comparative 

 Zoology at Harvard University, and of W. W. Welsh and Lewis 

 Radchffe, of the United States Bureau of Fisheries, the results of the 



Astroscopus guttatus, 20 mm. embryo. 

 Drawn from specimen by Bruce Horafall. 



