ENTEROPNEU.s I A 583 



formation of the walls of the body cavity as gastric divcrticula, 

 are all characters which point to a connection with Echinodcrm 

 larvae. 



On the other hand the eye-spots at the end of the pnt-oral 

 lobe 1 , the contractile band passing from the oesophagus to the 

 l>ots (fig. 273), the two posterior bands of cilia, and the 

 terminal anus arc all trochosphere characters. 



The persistence of the pne-oral lobe as the proboscis is 

 interesting, as tending to shew that Balanoglossus is the sur- 

 viving representative of a primitive group. 



BIBLIOGRAPHY. 



(567) A. Agassiz. "Tornaria." Ann. Lyceum Nat. Hist. \\\i. New York, 

 1866. 



(668) A. Agassiz. "The History of Balanoglossus and Tomaria." Mem. 

 Amer. Aead. of Arts and Scien., Vol. IX. 1873. 



(669) A. Gotte. "Entwicklungsgeschichted. Comatula Mediterranea. " Arckiv 

 fur mikr. Anat., Bd. XII., 1876, p. 641. 



(570) E. Metschnikoff. " Untersuchungen iib d. Metamorphose, etc. (Tor- 

 naria)." Zeit.fiir wiss. Zool., Bd. XX. 1870. 



(571) J. Miiller. " Ueb. d. Larven u. Metamor. d. Echinodcrmen." Berlin 

 Akad. t 1 849 and 1850. 



(572) J. W. Spengel. "Bau u. Entwicklung von Balanoglossus. Tagtbl.d. 

 Nalurf. Vert. Afiinchen, 1877. 



1 It would be interesting to have further information about the fate of the thicken- 

 ing of epiblast in the vicinity of the eye-spots. The thickening should by rights be the 

 supra-ocsophageal ganglion, and it does not seem absolutely impossible that it may give 

 rise to the dorso-median cord in the region of the collar, which constitutes, according 

 to Spengel, the main ganglion of the adult. 



