160 



JMEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



111 r-ytoplasiiiic differentiation, as distinct from the organelles contained 

 within it. the genns Gymnodiuiam exhibits both the shnplest as well as the most 

 advanced conditions found within the Gymnodiniidae, if not indeed within the 

 G}annodinioidae. The simplest type is shown in G. minor \\T.th its minute proto- 

 plasmic body surrounded by a thin perii:)last (fig. X, 12). The most advanced 

 type is that found in G. dogieli, with its thickened ectoplasm consisting of two 

 distinct la^^ers comi^letely surrounding the body and its distinct groups of 

 vacuoles, refractive bodies and radial rodlets, and its well developed pusules 

 (fig. V) . Its ectoplasm resembles that in many of the ciliates, the alveolar layer, 

 however, being at the surface of the body instead of separated from it by a 

 layer as is usual with the Ciliata. The superficial location of the alveoli gives 

 a bossed surface to these organisms which is very characteristic. 



;.;•• -"^ 



Fig. W. 1, 2. Gymnodinium lira sp. nov. X 477. 1. External form only, showing the ridges of the body. 

 2. Optical section of hypocone showing the structure of the cytoplasm. Note vacuoles surrounding nucleus 

 and the food body. 3. Amphidinium ciicurbita sp. nov. X 500. Superficial structure of the body onh', showing 

 the furrows and striations of the surface. 



The surface of the body in Gymnodinium presents nearly all the modifica- 

 tions found within the GAmmodinioidae. In the subgenus Gymnodinium, 

 containing the prunitive or more generalized species, surface striae or other 

 markings are relatively rare (fig. X) . One species in that group, G. herbaceum 

 (fig. Y, 17), shows a few, rather widely separated striae on the hypocone only; 

 G. sulcatum has the hypocone marked by a few furrows, and G. confracfum the 

 same markings on the epicone. In the subgenus Lineadinium (fig. Y) each 

 species shows a tA*i3ical and fairly constant striate surface. The striae may 

 be distinct lines or linear series of short rodlets, and usually vary somewhat in 

 number on epicone and hypocone. In all the species carefully observed these 

 striae are blue green, as are also those in the next subgenus. "When pigment 

 is present it is found to collect along the surface striae as in G. ruhrutn (pi. 8, 

 fig. 85). This is a condition more frequently met with, however, in Gyrodinium. 



