76 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



Spore formation in NodUuca is brought about by a rapid multiplication of 

 uur-lei without correspondius; cytoplasmic divisions. These nuclei retain their 

 position on one side of the spherical body. With the completion of the division 

 of the nuclei small buds of cytoplasm are formed projecting from one side of 

 the parent cytoplasm, each of which contains a single nucleus. These form 

 the flagellated "spores" which are possilily gametes, which remain attached to 

 the parent cell for some time before their liberation. 



In the life cycle of Gymnodinium lunula an analogous stage to the spore 

 production of Noctiluca may be found in the Pi/roctjsfis stage, when the body 

 divides into many erescent-shaj)ed individuals, each of which passes through a 

 further process of division (fig. I) producing small G ij tn nod iuium -like flagel- 

 lates which seem to be equivalent to the swarm spores of Noctiluca, and may, 

 like them, be gametes. Whether this rapid multiplication is preceded by conju- 

 gation is undetermined. 



In other groups of Protozoa where the life cycle has been followed out with 

 some degree of thoroughness it has been found that conjugation is usually fol- 

 lowed by rapid nmltiplication of the nuclei, resulting in the production of 

 numerous individuals. In Coccidium scJiuhergi (Schaudiun, 1900) this process 

 is not imlike that followed in Gymnodinium lunula as far as the production of 

 the crescent-shaped spores. In the well-known life cycle of the malarial para- 

 site, Plasmodium vivax (Schaudinn, 1902), the same conditions are found. 

 Conjugation in Paramecium, among the ciliates, is followed by a comparable 

 phenomenon, though here the number of individuals produced is relatively few 

 (Doflein, 1911). 



While no indisputable evidence can be offered on the subject of conjugation 

 in the dinoflagellates, yet these comi^arisons are suggestive. It is highly j)rob- 

 alile that a process sunilar to that outlined for Noctiluca may also take place 

 in the Pyrocystis stage of other dinoflagellates. 



A few instances may be found in the literature of so-called conjugation in 

 both the thecate and non-thecate dinoflagellates, Init these have too much doul)t 

 attached to them to be accepted without further verification. The first of these 

 was figured by Stein (1883, pi. 17, figs. 25-28) for Ampludinium lacustre. 

 These figures are identical with what have since been found to be division stages 

 in these forms, the two moieties still remaining attached to each other near the 

 region of the ends of the girdle (figs. L, jSI). 



Among the thecate dinoflagellates Joseph (1878) has reported conjugation 

 for Peridinium stygium, and Zederbauer (1904) for Ceratium MrundineUa. In 

 the latter case Zederbauer has figured a process similar to that found among 

 the conjugate algae. A conjugation tube is thrown out from the ventral sulcal 

 region of each of two individuals. These tubes meet and fuse into a zygospore, 

 the protoplasmic contents of each cell flowing into it. These zygospores become 

 free and have the appearance of the usual thick-walled, encysted forms of the 

 dinoflagellates. Nothing comparable with this phenomenon has as yet been 

 discovered in the unarmored Dinoflagellata. 



