ENTEROPNEUSTA. 583 



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

 are all characters which point to a connection with Echinodcrm 

 larvae. 



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

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

 eye-spots (fig. 273), the two posterior bands of cilia, and the 

 terminal anus are all trochosphere characters. 



The persistence of the prae-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.\u\. New York, 

 1866. 



(568) A. Agassiz. "The History of Balanoglossus and Tornaria." Mem. 

 Amer. Acad. of Arts and Stien., Vol. IX. 1873. 



(569) A. Gotte. " Entwicklangsgeschichte d. Comatula Mediterranea." Archiv 

 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. M tiller. " Ueb. d. Larven u. Metamor. d. Echinodermen." Berlin 

 Akad., 1849 and 1850. 



(572) J. W. Spengel. "Ban u. Entwicklung von Balanoglossus. Tagebl. d. 

 Naturf. Vers. Miinchen, 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-oesophageal 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. 



