210 HIROSHI OHSHIMA 
of the three dorsal tentacles, while still on the fourth day the 
ventral two retain their original interradial position, their 
bases, however, beginning to approach the mid-ventral radial 
canal. According to Kdwards (12, p. 216) the feature is quite 
different in H. floridana. Here on the fourth day each 
TEXT-FIG. 4. 
g Iv 
Cross-sections cut at the height of the ring canal, to show the 
gradual displacement of primary tentacles. A. Doliolaria, 
reconstructed from several sections. B. Metadoliolaria. C. Still 
advanced metadoliolaria. x 200. ep=epineural canal; g = 
gut; le = left enterocoele ; /v = left ventral radial canal ; mv = 
mid-ventral radial canal; re=ring canal; re= right entero- 
coele ; rv = right ventral radial canal ; /,,, = primary tentacles ; 
» = ventilating apparatus. i 
of the mid-ventral and the left dorsal radial canals produces 
a tentacle on the right side, and each of the paired ventral 
radial canals sends out one on the dorsal side. Of these four, 
the former two seem to be the first to develop. The fifth appears 
