KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 413 



r»iolioli (1870) describes two new species of Noctiluca, N. omogcnca and 

 A', luicificd, but neither appear to be distinct from N. scuitiUans. 



There appears thus to be but a single species, Noctiluca scintiUans 

 (Macartney), in this genus. It is evident that this name is the only one de- 

 fensible under the code of nomeuclature. It is the type of the genus Noctiluca. 



Comparisons. — It is obvious that the adaptation of Noctiluca to passive 

 flotation by hydrostatic vacuoles has brought about profound modification of 

 structure. The locomotor organs, the two flagella, are no longer functional as 

 a rotator and propellor respectively. The longitudinal flagelkmi is hidden in 

 the reentrant atrium and the transverse one is reduced to a mere prehensile 

 tooth. With the degeneration of the latter the girdle disappears, except for 

 its proximal region, and the separation between epicone and hj'^^ocone is lost. 

 The sulcus is developed as a large cytostome and the form of the body, as a 

 result of inflation by the vacuoles, loses all marked dinoflagellate characteristics, 

 except as indicated by the sulcus. 



The tentacle in its location, structure, and function is foreshadowed or 

 paralleled by the pseudopodium-like tentacle of Gymnodiniwm pseudonoctiluca, 

 the tentacle of Pavillardia, the incipient prod of Proterythropsis, and the fully 

 developed one of Ert/thropsis. This tentacle of Noctiluca can not be the homo- 

 logue of these structures and at the same time represent the transverse flagellmn, 

 as Biitschli (1885) proposed, since the transverse flagellum is present in other 

 tentaculate dinoflagellates and is fully functional. It is rather, as Kof oid ( 1919) 

 has shown, not a homologue of either flagellmn, but a derivative of the margin 

 of the sulcus as are the other tentacles of the dinoflagellates. There is no 

 satisfactory evidence that the tentaculate dinoflagellates form a coherent family, 

 but rather that they are of independent origin in several families. It is still 

 pi'obable, however, that the tentacles are to be regarded as homologous organs 

 throughout the series. 



