KOFOID AND SWEZY: UNARMORED DINOPLAGELLATA 113 



Description. — The body is stout fusiform, widest posteriorly, apex acuminate, tapering some- 

 what anteriorly, its length, including the tentacle, 3.8 transdiamcters at the girdle. It is sub- 

 cireular in cross-section but flattened somewhat ventrally in the anterior half. The hypocone is 

 3.3 transdiameters in length or 7 times the length of the epieone. The antapex is contracted 

 to a stout subconical or slender acuminate horn 0.5 to 1 transdiameter in height. The epieone is 

 comparatively minute, about 0.5 transdiameter at the girdle in lieight, subconical with convex 

 sides and blunt antapex, which in one case was slightly bifurcated without any accompanying 

 evidences of mitosis. 



The girdle is rudimentary, scarcely visible, and in individuals from collections which have 

 stood for some hours in the laboratory it wholly disappears. It is located far anteriorly at 0.15 

 of the total length of the body from the apex. It lies in a transverse plane and is developed 

 from the pore of the transverse flagellum distally only about 0.25 of the circumference. It is 

 the merest shallow rounded trough, without marked lips, ridges or list of any sort. The trans- 

 verse flagellum lies habitually in this girdle and continues in its plane to encircle the body. Its 

 fuU length completely encircles the body, though its distal end is sometimes spasmodically thrown 

 anteriorly and brought back into place. As the animal grows moribund this flagellum falls away 

 from its habitual position as in other dinoflagellates. It is a very narrow ribbon with well marked 

 basal axis and characteristic short undulations which travel incessantly towards its distal end. 



The fully developed sulcus runs from the flagellar pore anteriorly to the apex as a rather 

 deep trough, sometimes laterally overhung by the edges. It is straight, shows no separate pore 

 for the longitudinal flagellum and encloses the base of the stout tentacle, which merges into its 

 dorsal wall. A denser tract pa.sses posteriorly for a short distance into the cytoplasm from its 

 base. The sulcus does not extend posteriorly upon the hypocone. 



The longitudinal flagellum of this species has been I'educed to a short lash, and in its place 

 an anteriorly directed tentacle has been developed, which is the most striking characteristic of 

 the organism. This is a stout rodlike structure projecting about 0.25 of the length of the body 

 beyond the apex. It is cylindrical, of equal caliber throughout and terminates bluntly in a 

 squarish tip. A differentiated axial core of greater density traverses its entire length. 



The cell contents consist of a very indistinct nucleus located in the anterior half of the body 

 and food masses. The nucleus is ellipsoidal in form with its major axis running from the right 

 anteriorly to the left posteriorly. It is traversed longitudinally by coarse, nodulated chromatin 

 threads, about ten on one face. Posterior to this, and flUiug the posterior half of the hypocone, 

 is a large, subspheroidal, dull orange-yellow food body with several adjacent smaller spheres. 

 In some individuals this is broken up into a number of smaller spherules. In still others a cloud 

 of small, rounded, elliptical, or rodlike, dark olive granules surrounds the anterior half of a food 

 body in a broad irregular band. A cluster of highly refractive, spherical oil droplets fills the 

 antapical cone and several linear greenish rodlets, or a single large stout one, lie near the flagellar 

 pore. The pinkish jjusule lies posterior to the pore in the median line and is connected with the 

 pore by a slender canal. The general color of the cytoplasm is a greenish grey, with a yellowish, 

 or ochraeeous tone anteriorly. There are no striae on the surface and no scattered vacuoles or 

 droplets of pigment. 



Dimensions. — Length, 54/^; transdiameter, at the girdle, 13m, at the widest 

 part of the hypocone, 23i^ ; length of tentacle beyond the apex, 16/^. 



Variation. — The principal variations noted are due to the size of the in- 

 gested food bodies. When this is large the posterior third is somewhat dis- 

 tended. In one ease the antapex was nnich more acuminate than in the others. 

 It is not metabolic to any considerable degree, the only changes of this sort 

 noted being a tendency to form a constricted ring around the base of the tentacle. 



