300 



ENTEBOPNEUSTA. 



an affinity to the Tunicnta by the mode of respiration. This in- 

 teresting worm was discovered by Delle Chiaje, and its organization 

 and development have been recently investigated by Al. Agassiz and 

 Kowalevski [more recently by Bateson, Q. J. Mic. 8ci. 1884] (fig. 241). 



The most inte- 

 resting point about 

 this form is the 

 structure of its 

 larva, which renders 

 its relationship to 

 the Echinodermata 

 probable. The larva 

 was described by J. 

 Miiller as Tornaria, 

 and was regarded 

 by him as an Echi- 

 noderm larva. It 



FIG. 241. Young Ealunoglosmts, strongly magnified. Pr, Pro- (Joes, in fact, possess 

 boscis, the numerous branchial slits are visible. . , . . , r 



a double band or 



cilia, like Bipinnaria. Of these two rows of cilia, one, the praeoral, 

 forms a ring round the prse-oral lobe, while the other is larger 

 and runs in a more longitudinal direction so as almost to join the 



former near the 

 apical pole. There 

 is also a transverse 

 piw-anal ring of 

 cilia (fig. 242, a, b). 

 Internally a diverti- 

 culum of the ar- 

 chenteron gives rise 

 to an independent 

 sac forming the 

 water-vascular sys- 

 tem, while two 



from the side ; 1. from the dorsal surface. O, mouth ; A, P alrs f dlvei'tlCllla 

 anus ; S, apex, W, rudiment of water vascular system ; C, furnish the first 

 heart ; P, P', peritoneal sacs. 



rudiments of the 

 body cavity. A pulsating heart is developed from a thickening of 



"The History of Balanoglossus and Tornaria." Memoirs of tJtc Aincricmi, 

 Art/r/// of Arts and Xcimcc.t, Vol. IX.. 1873. E. Metschuikoif. Zritsclir. 

 f. wisscnstfi. Zool.. Tom XX.. 1870. 







a -/i 7, ^^-^ P ' 



FIG. 2l2,n, l. Tnrmirin larva (after E. Metschnikoff). u, Seen 



