340 bulletin: museum of comparative zoology. 



is that of crowded but independent non-attached cells which upon 

 their release are wholly independent of one another. In Gonyaulax 

 series the daughter cells remain broadly attached and the thin pellicle 

 upon the surface of each is transformed into the sutured theca with 

 the plates normal to the region, while those parts of the theca normal 

 to the surface of the cell body as yet unexposed because of the proto- 

 plasmic continuity of adjacent schizonts, remain unrepresented in 

 the transforming pellicle. Moreover in Gonyaulax series these schiz- 

 onts do not soon lose their protoplasmic continuity but they form the 

 same type of pellicle as in Pyrophacus on their exposed surfaces and 

 this is then progressively instead of synchronously differentiated by 

 suture lines into the Gonyaulax type of theca. 



The differences in size of the schizonts and their progressive differ- 

 entiation of the theca distally in G. series indicate that the schizogony 

 may not be coincident in all members of the forming chain but that 

 division is irregular and localized and that the later divisions result 

 in the formation of the more distal and smaller members of the chain. 

 Assuming the chain to be complete it appears both on the ground of 

 dimensions and of the peculiar twisting of the three centrally located 

 members from the common axis of the remaining eight, that the chain 

 falls into three regions, two distal groups of four each and a central 

 group of three large individuals, and that the distal groups represent 

 later generations of descent than the larger central ones. 



The previous stages and those subsequent to the one here observed 

 can only be conjectured. The normal course would be that the con- 

 strictions separating the individuals should deepen and finally result 

 in the complete separation of the schizonts and the completion of the 

 individual thecae. The presence of such an abundant supply of 

 starch grains (st. gr. Plate 2, fig. 3) in each cell arranged in a broad 

 equatorial zone about the nucleus (n.) is indicative of predominant 

 synthesis, that is, of a condition favorable to rapid growth. The 

 sheath of incomplete thecae surrounding the dividing mass of cyto- 

 plasm is a striking instance of the plasticity of the Dinoflagellate 

 theca. The rigid conformity of each partial theca to the specific 

 type is an even more striking illustration of the expression of the 

 structure of the individual, in this case a single cell, while still in 

 cytoplasmic but not nuclear continuity, with its sister individuals. 

 The cytoplasm is scarcely individualized, at least by discontinuity, 

 but the nuclei and the discrete skeletal structures in so far as 

 opportunity is afforded for their formation attain their complete 

 individual realization. 



In a recent paper Apstein (1910) has described a process of budding 



