'■l')'2 riiircrsihj of Cnliforiiiii Piihliialions in Zoology. [Vol.4 



whose habit is strongly siifriicstive of a senile condition and whose 

 cell wall is apparently thickened by tlic accrcliori.s of lon^-con- 

 timied growth. Obviously such structure inust profoundly affect 

 both iiietabolisiii and flotation, for it cuts down the access of light 

 to the chroniatophnres of the cell on the one hand and on the other 

 affects both specific gravity and specific surface. 



3. Transfer of llie anccslral Uiccn in sdiizorjoinj.—AHcxwal 

 reproduction in Ccratium as in most Dinoflagellates and the flag- 

 ellates generally, is accomplished by binary fission, though the 



Fig. 9. — Dorsal view of Crrntinm vulfur, a form with short horns in 

 chain showing compensatory character of newly formed thecal moieties, to 

 wit, the two thecal halves liotwecn the dotted fission lines. The weight of 

 the lines represents the relative thickness of the walls. X -iO. 



possibility of multiple spore formation can not be excluded. In 

 the binary fission of Ccnitlinii. as has been shown in detail by 

 Lauterborn ('95) for C. hiniitdindla, and as may be seen in 

 most recent schizonts (figs. 5 and 6), the plane of fission is not 

 transverse but passes obliquely across the body from the right 

 anterior to the left posterior margin, separating the parental 

 theca into two parts. The anterior part includes the apical horn 

 and precingular plates 1" and '1" } and postcingular plates 1' ", 

 2'" and 3'" with the left half of the girdle which is included 

 between the two series of plates. On tlie dorsal face the suture 



