1920] Kofoid: New Interpretation of thi Structure of Noctiluca 325 



erroneous orientation in his Lehrbuch. Comparative morphology and 

 observations on the living animal establish the posterior location of 

 the tentacle (see Kofoid and Swezy, 1917). 



The species of Erythropsis mentioned have the following structural 

 features. There is a girdle with bordering paraeingular lines sharply 

 displaced posteriorly near its distal end, making one turn about the 

 body. In it lies the transverse flagellum, thrown out of the girdle in 

 our figure I. The sulcus is a highly modified structure extending 

 anteriorly upon the epieone in a more or less spiral apical loop. Pos- 

 teriorly it expands into a deep recess, the tentacular chamber, from 

 which protrudes the cylindrical, sometimes capitate tentacle, or prod. 

 Adjacent to the base of this prod in the upper part of the chamber is 

 the insertion of the longitudinal flagellum. which sometimes can not 

 be found, and is usually short and difficult to see. Here also the 

 tentacle is an outgrowth of the posterior part of the sulcus, specialized 

 as the tentacular chamber, posterior or adjacent to the longitudinal 

 flagellum. 



It is obvious, from this comparative analysis of tentacle-bearing 

 dinoflagellates, that if Noctiluca is one of the Dinoflagellata it will 

 not be exceptional in the possession of a tentacle, and also that this 

 interpretation involves the presence in Noctiluca of the girdle, sulcus, 

 and of the two flagella, as well as of the tentacle. We will now proceed 

 to the demonstration that these organs are present in Noctiluca. 



For the proper understanding of the morphology of Noctiluca it 

 is essential to so orient its body that a consistent terminology of 

 planes and axes, as well as of organs is both feasible and logical. This 

 is accomplished by considering that the deep straight groove is the 

 sulcus and on the midventral line. It follows then that the tentacle 

 is in this line and we locate it at the posterior end of the sulcus as 

 in other dinoflagellates, and not anterior as Butschli (1885) located 

 it. Granted these points, it follows perforce that the face opposite to 

 the groove is the dorsal one and that the anterior pole is that towards 

 which the "superficial ridge" of Altaian (1872) is extended, this 

 "ridge" being in fact the apical section of the sulcus. The girdle must 

 then be looked for at right angles to and to the left of the sulcus 

 (right of fig. 3, pi. 18). The transverse flagellum would be located 

 in this girdle if normally developed and would take its origin at or 

 near its junction with the girdle. The longitudinal flagellum would be 

 found running lengthwise in the sulcus, with its origin in front of 

 the tentacle and near or posterior to the junction of girdle and sulcus. 



