46 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



One cannot work with tlie marine iinarraored Dinoflagellata for even a short 

 time without being struck by the fact that the majority of the individuals ob- 

 served show evidences of holozoic nutrition, in tlie G}^nnodimoidae at least, and 

 that the number actually containing chromatophores is relatively small through- 

 out the entire Dinoflagellata. Contrary to West's statement, it is jjrobable that 

 a large number of them have not holophytie but saprophytic or holozoic nutri- 

 tion. It is notable also that a few forms, as Arnphidiniiim steini, may possess 

 chromatophores and at the same time show the presence of foreign bodies in 

 the cytoplasm (Stein, 1858-59). This has been true in our own material also 

 (pi. 4, fig. 44; pi. 5, fig. 50), though the actual ingestion of foreign organisms 

 has not been observed. 



The cell contents of an alga consist of nucleus, chromatophores, pyrenoids, 

 starch grains or related assimilates, and perhaps a few oil globides. On the 

 other hand, the presence of distinct chromatophores of the typical algal form 

 is a comparatively rare occurrence in the dinoflagellates, even in the thecate 

 forms, where the ingestion of solid particles of any considerable size would 

 appear to be a difficult if not impossible procedure. The evidences for holozoic 

 nutrition lie in the presence of food bodies, often of recognizable organisms, 

 within food vacuoles in the cytoplasm, and the accumulations of the products 

 of metabolism in the forni of oil globules, vacuoles, refractive granviles, and 

 rodlets in the central or peripheral plasma. These, correlated with the absence 

 of chromatophores, would seem to offer conclusive evidence of holozoic nutrition 

 in the greater number of species of the unarmored tyi^e. 



The genus Ampliidinium is probably more nearly holophytie throughout its 

 range than any other genus as a whole. A few apparent exceptions are found 

 here, however, as in A. steini, mentioned above. Stein has figured this species 

 with definite organisms in the body as well as chromatophores, though the latter 

 are smaller than those in individuals without ingested food bodies. It may 

 be that this indicates a periodic recurrence or at least facultative occurrence 

 of both types of nutrition. Evidences of a similar condition may be noted in 

 A. scissum (pi. 2, fig. 22). A. cucurhifeUa (pi. 1, fig. 6) shows undoubted 

 evidences of holozoic nutrition. Two large masses are present in the cytoplasm, 

 one surrounded l)y a water vacuole as though recently ingested. In A. cucurhita 

 (pi. 1, fig. 9) the body is filled with radial rodlets and large masses, one of which 

 lies in a vacuole, interspersed with refractive granules, the whole presenting 

 an appearance hardly comi^atible with holoph}i:ic nutrition. Other species in 

 this genus which show some slight evidences of holozoic nutrition are .4. crassum 

 (fig. U, 18), A. sulcatum (fig. U, 10), and A. vasculum (pi. 4, fig. 36). 



In the genus Gymnodinium a relatively smaller nmnber of species occurs 

 which possess undoubted chromatophores. Most of these are found in the more 

 generalized group, the subgenus Gymnodinium strictu sensu. Here also, as in 

 Amphidinium, the two t}i)es of nutritit)u are occasionally found associated in 

 the same species, as in Gymnodiiiium fidgens (fig. X, 30), G. agile (pi. 3, fig. 

 31), and in G. herhaceuvi (pi. 4, fig. 44). 



