KOPOID AND SWEZY: UNARMORED DINOPLAGELLATA 399 



pores just below the distal junctions. The transverse flagella seldom have a length greater than 

 0.5 turn around tlie body and the posterior tlagella are usually about equal to the length of a 

 single zooid. These usually do not lie in the sulcus, but are thrown out at a slight angle. The 

 longitudinal flagelluni of the posterior zooid may be considerably longer than the other longi- 

 tudinal tlagella. 



The nucleus is a spheroidal body, tilled with moniliform chromatin strands. It is generally 

 found near the center of the body, slightly to the right of the sulcus. Its transdiameter is 

 about 0.39 transdiameter of the body in length. The number of nuclei usually lags behind the 

 number of zooids in a cliain, one being present in a two-zooid chain, two in four zooids, and 

 four in eight zooids, showing a lack of synchronism in the division of nuclei and cytoplasm. 



The plasma is translucent, finely granular and generally abundantly tilled with nematocysts, 

 food bodies and vacuoles. The nematocysts vary in number and arrangement in different 

 individuals. This species is an omnivorous feeder, appropriating almost an.y small organism 

 found in the plankton, such as crustacean larvae, copepod eggs, other dinotlagellates, as 

 Oonyaulax, Peridinium, and Diplopsalis, with other organisms indistinguishable owing to their 

 advanced stage of digestion. It is evident from the large size of many of the food bodies thus 

 taken in that two or more individuals of the chain must cooperate in the process of ingestion. 

 The ejection of solid particles has been observed from the sulcus at the region of the posterior 

 pore. This takes place very quickly, the cytoplasm closing up to its normal appearance in about 

 thirty seconds. 



The plasma has a rosy tint, varying sometimes to pale green or almost colorless. The depth 

 of the rose color varies greatly in diiferent individuals, and is more pronounced in the peripheral 

 zone of cytoplasm. The surface of the epicone is generally smooth, that of the hypocone striate 

 and furrowed, about ten striae or ribs on 0.5 transdiameter. The surface between the striae 

 may be raised into smoothly rounded ridges. 



Activities. — These are very active organisms, tlieir incessant motion making 

 any attempt to determine the coordination or lack of it, in the movements of 

 the diiferent flagella, a matter of great uncertainty. When first placed under 

 the microscope the progression is mainly in loose, anticlockwise spirals with 

 ouly occasional clockwise rotations, varied with jerking motions of the anterior 

 end upward, and occasionally reversing its spiral direction. Either the ventral 

 or dorsal side may be uppermost when (juiescent. 



Coordination in the movements under the cover glass of the different sets 

 of flagella is lacking at least part of the time. One or two of the transverse 

 flagella may be in active motion wdth the others only faintly or not at all motile. 

 "When all are moving at the same time the rate of motion is not the same for 

 all nor does motion l)egin in each at the same time. This is equally true of the 

 longitudinal flagella. 



Under the brilliant illumination necessary for microscopic work the 

 organism soon rounds u]) to a spheroidal form, the girdles becoming completely 

 ol)literated and motion ceasing gradually. With cytolysis and dissolution of 

 the body, the nematocysts are usually discharged a few seconds after the 

 breaking down of the body wall. 



DiMKNSiONS.— Length of individual zooid, 25-45/^; length of 4-zooid chain, 

 1 lO/j ; transdiameter, 70-90j"; diameter of nucleus, 25-30^; length of nematocysts, 

 10-20/^. ' • 



