146 



Mr. W. F. R. Weldon. On a [Mar. 3,. 



Stevenson, Thomas, M.D. 

 Teale, Thomas Pridgin, F.R.C.S. 

 Tenison- Woods, Rev. Julian E., 



M.A. 

 Thin, George, M.D. 

 Tidy, Professor Charles Meymott, 



M.B. 



Todd, Charles, M.A. 



The following Papers were read : 



Tomlinson, Herbert, B.A. 



Topley, William, F.G.S. 



Ulrich, Professor George Henry 



Frederic, F.G.S. 

 Walsingham, Thomas, Lord. 

 Whitaker, William, B.A. 

 Yeo, Professor Gerald F., M.D. 



I. " Preliminary Note on a Balanoglossus Larva from the 

 Bahamas."' By W. F. R. Weldon, M.A., Fellow of 

 St. John's College, Cambridge. Communicated by Prof. 

 M. Foster, Sec. R.S. Received February 15, 1887. 



In October last, during a visit to the Island of Bernini, on the 

 western edge of the Bahama bank, an organism was constantly found 

 in the tow-net which closely resembled the larva of Balanoglossus 

 recently described by Bateson,* 



In the youngest stage observed, this creature has an elongated 

 cylindrical body (about 0*8 mm. long by 0*4 mm. broad) with rounded 

 ends. At the anterior extremity are two eye-spots, while near the 

 posterior is a large and powerful ring of cilia. An anterior region is 

 separated from the rest by a deep transverse groove ; more than this 

 cannot be made out by examination of entire specimens.! A little 

 later, a second shallower groove appears behind the first, marking off 

 a smaller middle region of the body from the larger anterior and 

 posterior divisions. An idea of the shape of the body, just before the 

 appearance of the second transverse groove, may be gathered from 

 the nearly median longitudinal section (fig. 1). In this section the 

 mouth is seen to lie in the first transverse groove, on the ventral side 

 of the body ; it leads to a well-developed alimentary canal, ending in a 

 median posterior anus, not seen in the figure. On each side of the 

 alimentary canal lie two sections of body cavity ; the first (fig. 1, II) 

 can hardly be spoken of as a cavity, its lumen being never con- 

 spicuous, and often obliterated ; behind this is a well-developed pos- 

 terior cavity (III)- The body cavities of the two side3 are separated 



* 'Koy. Soc. Proc.,' vol. 38, 1885, p. 23 ; and ' Quart. Journ. Microsc. Sci.,' 1885 

 and 1886. 



f I regret that my observations on the living larva are most imperfect. Owing to 

 my want of experience in protecting delicate organisms, after capture, from a tropical 

 sun, I was frequently obliged to preserve the material obtained in an open boat, 

 where microscopic work was impossible. 



