156 AVILLIAM BATESON. 



blance are more tliau superficial, especially when it is re- 

 membered that the adults of both animals possess essentially 

 similar branchial structures which, beyond the Chordata, are 

 otherwise without parallel in the animal kingdom. There are, 

 of course, many and great difficulties which preclude any 

 assumption of relationship between them, notably the absence 

 of any regular notocliord in Balanoglossus. 



On this occasion it is not profitable to discuss these ques- 

 tions at greater length. When, however, the later develop- 

 ment of this form has been described, it may perhaps be 

 possible to arrive at more definite conclusions. 



In closing this paper I have to thank Mr. Sedgwick and 

 Mr. Weldon for rendering me much valuable assistance and 

 advice in connection -with it. 



List of Papees bepekred to. 



1. — Agassiz, Alex., " The History of Balanoglossus aud Tornaria," 'Mem. 



of the Amer. Acad./ vol. ix. 

 2. — GoTTE, Alex., "Vergl. Entw. d. Comatula," 'Archiv f. Mikr. Anat.,' 



xii, 1876. 

 3. — Hatschek, B., "Stud. iib. Eutw. d. Amphioxus," Claus's ' Arbeiten,' 



Wien, 1881. 

 4. — Leidy, J., "Ou B.i]anoglossus," 'Proc. Acad. Nat. Sc. Philadelphia,' 



1881. 



5. — Metschnikopp, "El. lib. d. Metam. eiuiger Seethiere," ' Z. f. w. Z.,' 

 20, 1870. 



6. — Metschnikopp, "El. iib. d. Syst. Stell. v. Balanoglossus," 'Zool. 

 Ausz.,' 1881. 



7. — Spengel, " Bau u. Entw. v. Balanoglossus," 'T.igeblatt d. Naturf. 

 Ver. Miinchen,' 1877. 



