Development of Holothuria Floridana Pourtales 227 



A. Discussion of Literature. 



Joh. Miiller, 1853, reports the first pedicel in the "Auricularia 

 mit Kugeln," as from the mid-ventral radial canal posteriorly and 

 to the right. Previous to my work (1889, 1907) all other authors, 

 Krohn, 1851, in Cucumaria planci; Danielssen and Koren, 1856, 

 in Holothuria tremula ; Agassiz, 1864, in Psolus fabricii ; Kowalev- 

 sky, 1867, in Cucumaria kirchsbergii, Cucumaria planci and Phyl- 

 lophorus uma; Selenka, 1876, and Ludwig, 1891a, in Cucumaria 

 planci, and Ludwig, 1898, in Phyllophorus urna, describe the first 

 two pedicels as developing in a pair from the posterior end of the 

 mid-ventral radial canal. Ludwig notes the origin of the first pair 

 in the fourth day and that these pedicels are truly developed on the 

 eighteenth day. Danielssen and Koren, 1856, record in an embryo 

 of Holothuria tremula of the thirty-fourth day, the appearance of 

 the second pair of pedicels above the first, and on the fifty-sixth day, 

 the third pair. In the last stage also, dorsal papillse are seen here and 

 there. Ludwig, 1891, describes in Cucumaria planci, the third 

 pedicel arising to the left of the mid-ventral radial canal, in front 

 of the two primary, on the forty-fifth day. The fourth pedicel does 

 not appear until the eighty-fourth day and then still further forward, 

 but to the right. The fifth pedicel arises on the hundred and eleventh 

 day anteriorly and ventrad from the left dorsal radial canal. There- 

 fore, the same radial canals from which the primary tentacles devel- 

 oped serve for the budding of the first pedicels. Ludwig, 1898, 

 states that in Phyllophorus urna the third pedicel appears before, 

 and the fourth pedicel behind the first two. In this fashion a zigzag 

 line is formed. At two and one-half months the larva possesses two 

 more mid-ventral pedicels, and two from each lateral ventral radial 

 canal, but none in the bivium. 



Becher, 1908, makes various suggestions as to the possible phylo- 

 genetic significance of this marked precocity in the ontogeny of the 

 pedicels from the mid-ventral radial canal, without, however, coming 

 to any satisfactory conclusion. Because the appendages increase 

 with growth, Herourard, 1901, believes that a single species passes 

 successively through stages characteristic of Ocnus, Cucumaria and 

 Semperia, and, therefore, the first and last are synonyms of 

 Cucumaria. 



