The Early Stages in the Development of 

 Balanoglossus (sp. incert.). 



By 



William Bateson, B.A., 



Scliolar of St. John's College, Cambridge. 



With Plates XIII, XIV, XV and XVI. 



Through the great kindness of Dr. W. K. Brooks and the 

 Council of Johns Hopkins University, I was permitted to avail 

 myself during the summer of 1883 of the facilities offered by 

 the Chesapeake Zoological Laboratory, which was then situated 

 at Hampton, Virginia. My best thanks are due to Dr. Brooks 

 for the most valuable and manifold assistance which he gave 

 me, both in my work and otherwise, during my whole stay at 

 the Chesapeake Station. 



While resident at Hampton I had an opportunity of obtaining 

 a small species of Balanoglossus, which was to be found there 

 in great numbers, buried in the sand at about half tide. 



The characters of the adult animal agree very closely with 

 the description given by Agassiz of the species named by him 

 B. Kowalevskii; but as the species which I examined deve- 

 loped in a manner totally different from that which Agassiz has 

 described for B. Kowal ev skii, I am compelled to suppose that 

 the two animals are not identical. 



As will afterwards be shown, the points in which the anatomy 

 of this animal differs from that described by Agassiz are of such 

 a fundamental character that it is impossible to regard them as 



