456 

 6. Balanoglossus and Tornarla of New England. 



By T. H. Morgan. 



eingeg. 19. October 1892. 



Uuring the past summer of 1892, while at the Marine Laboratory, 

 at Wood's Holl, Mass., I made a further and successful attempt to clear 

 up the difficulty that had arisen as to the method of development of the 

 common Balanoglossus Kotvalevskii found on the New England coast. 



In 1873 Alex. Agassiz described the transformation of the 

 Tornarla found abundantly at times in the waters along the south 

 shore of New England, and most naturally referred the Tornarla to the 

 common Balanoglossus of the same coast. 



In 1883 and 1884 Bateson, working at the Chesapeake Zoologi- 

 cal Laboratory at Hampton, Va. (1883), and at Beaufort, N. C. (1884) 

 showed that Balanoglossus Kowalevskli in the Southern waters had an 

 abbreviated development, without the free swimmig Tornarla. 



It then became evident, that, either the New England Tornarla 

 did not belong to the B. Koivalecskll of the New England coast, or the 

 B. Kowalevskli had in the north an indirect and in the south a direct 

 development. 



In 1891 I pointed out that the mature eggs of the B. Kowalevskli 

 of Wood's Holl were of the same size as those of the B. Kowalevskli 

 of the Chesapeake, and that the eggs were larger than the 

 youngest and smallest of the New England Tornarla. From 

 this and from other facts the conclusion seemed to follow that B. Ko- 

 xoalevskll found at Wood's Holl (and by inference B. Kowalevskli of 

 New England) had a direct development. 



This conclusion was not entirely satisfactory for two reasons, first 

 because it was possible that B. Kowalevskli found at Newport by 

 Agassiz might be difi'erent from the Wood's Holl form, and secondly 

 because neither Agassiz nor I had been able to obtain the young of 

 B. Kowalevskli of New England. 



While on a short visit to Newport I examined, through the cour- ' 

 tesy of members of Prof. Agassiz's Laboratory, the Balanoglossus 

 found there, and satisfied myself, and others, as to the identity of this 

 form with the Wood's Holl individuals. 



Later, at Wood's Holl, I succeeded in finding in great numbers 

 the embryos of the New England Balanoglossus. 



On Sept. 18 1 first found these in the sand in Buzzard's Bay at 

 stages corresponding to stages D to H of Bateso n's paper. These 

 were still within the ^%% membranes. During the following week 

 I succeeded in getting, by the method described below, many hundreds 



