. Journal of morphology . my series is in-dicated. Each of the first four of the primary tentacles, so Avellinaugurated in the fourth day, is marked A, and the fifth, buddingin the fourth day, A5. Following this scheme of symmetry. Table Ipresent the details in the development of the tentacles from thesixth to the eighty-seventh days. After the seventh tentacle, the orderof appearance sometimes varies, but the serial numbers, given inDiagTam 1, follow the usual ontogeny. By the fortieth day, the sixth tentacle, small but developed (PLII, Fig. 10, KVd2) is clearly seen in the living holothurid.
. Journal of morphology . my series is in-dicated. Each of the first four of the primary tentacles, so Avellinaugurated in the fourth day, is marked A, and the fifth, buddingin the fourth day, A5. Following this scheme of symmetry. Table Ipresent the details in the development of the tentacles from thesixth to the eighty-seventh days. After the seventh tentacle, the orderof appearance sometimes varies, but the serial numbers, given inDiagTam 1, follow the usual ontogeny. By the fortieth day, the sixth tentacle, small but developed (PLII, Fig. 10, KVd2) is clearly seen in the living holothurid. Ithas evaginated from tho tentacular canal of the primary tentacledorsad from the right ventral radial canal just after it leaves theradial canal (Diagram 1, E. 6). One specimen of this age has alsothe bud of the seventh tentacle from the canal of the primary ten-tacle dorsad from the left ventral radial canal (L 7). The day whenthe bud of the sixth tentacle may have first appeared, I was not 218 Charles Lincoln Edwards. 9,IO A ^^ [^ A5 ^11 12 Diagram I. Order of development of thirteen of the twenty tentacles con-stituting the adult symmetry. The vertically hatched central oesophagus issurrounded by the circular canal of the water-vascular system, from whichthe five radial canals arise. The five radialia, and the five interradialia, arehatched diagonally. At the base of each radiale, the radial canal givesoff two tentacular canals to each side and then proceeds anteriorly, turningthrough the notch into the body-wall. The first tentacular canal to bedeveloped runs along the inner surface of the radiale-interradiale jointand the second, having been evaginated from the base of the first, goes along-side of the radial canal. At the anterior margin of the calcareous ring,the tentacular canals give off the ampullse and then terminate in the peltatetentacles. The ampulhie hang down behind the calcareous pieces, and, as theycome into view, are seen outlined against the cross-hatching
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