EGGS OF A NEW SPECIES OF NEMATOID WORM FROM 



A SHARK 



By G. A. MacCallum 



Of Baltimore, Md. 



On July 6, 1924, we examined at the United States Bureau of 

 Fisheries at Woods Hole, a large shark, G archarhinus commersoni, 

 and I found on the white under surface of the nose, in front of the 

 mouth, a curious figure, which appeared like a drawing made with 

 a fine pen with India ink. The figure was formed by a delicate 

 tracery of lines extending over a patch about 2iA inches by II/2. 

 We could not imagine why such a tracing should be there, and, 

 as nothing of the particulars could be made out with the naked 

 eye, I sliced off portions of the figure and placed them under 

 the microscope was surprised to find that the lines were made 

 up of black eggs laid in the grooves between the scales. We had 

 never seen anything like it before and were at a loss to know what 

 form could have laid them there, how it was done, and how they 

 were kept in place and not swept away when the fish made its way 

 through the water. Careful examination has failed to show any 

 female worm which could have laid them. 



Vertical and horizontal sections of the skin were made, after 

 decalcifying the scales with hydrochloric acid, and in these the eggs 

 were plainly seen to be those of some small worm, and attached 

 to the grooves between the scales by some transparent, very adhesive 

 glutinous material which surrounds them. They are dark brown, 

 almost black, where the shell is thickest, and are of an elliptical 

 form, measuring 0.10 mm. in length by 0.005 mm. in width. Ante- 

 riorly each has a closed orifice at the end of a short neck. 

 * Dr. N. A. Cobb, who was kind enough to examine them, thought 

 that they much resembled the eggs of 2'richocephalus dispar in 

 form, and later it was decided that they belong in all probability 

 to a member of the genus Oapillaria. Since it has been impossible 

 to find the female worm that laid them, the question arises as to 

 whether it may be that, as in the case of the common wild rat in 

 which a nematode of this general type lays eggs in fine lines over 



No. 2588. — Proceedings U. S. National Museum, Vol. 67, art. 16. 



29109 — 25 1 



