KOFOID AND RIGDEN: SCHIZOGONY IN GONYAULAX. 337 



Schizonts retaining a temporary connection in chain. Gymno- 



dinium geminatum. 

 Schizonts permanently associated in short chains (colony) with- 

 out much transverse constriction. Polykrikos auricularia. 

 Body of schizonts thecate. 



Parental theca retained and shared by schizonts. 



Schizonts detached at once upon fission. Gonyaulax spini- 

 fera, many species of Ceratium, Steiniella, Ceratocorys, and 

 most of the Dinophysidae. 

 Schizonts retaining connection for some time after fission. 

 By dorsal thecal attachment. Dinophysis geminate, Orni- 

 thocercus. 



By protoplasmic connection between distal end of girdle of 

 anterior schizont and apical pore of posterior one, estab- 

 lishing true chain formation. Many species, of Cera- 

 tium (C. candelabrum, C. vultur, C. palmatum), Gonyaulax 

 catenata. 

 Entire theca newly formed on schizonts. 



Parental theca shed by ecdysis. No chain formation. 



Prior to fission. Sometimes in Gonyaulax spinifera (see 



Schiitt, 1887) also in G. polyedra. 

 After fission, schizonts closely packed in parental theca but 

 not attached to one another. Pyrophacus horologicum. 

 Chains of schizonts formed with complete polar protoplasmic 

 attachment retained for some time. New theca on schizonts 

 formed progressively toward distal ends of chains. Gony- 

 aulax series. 

 The skeleton of the species here described is certainly not formed 

 until after division, if we may trust the evidence of the posterior mem- 

 ber of the chain. This, as appears plainly in the specimen (Plate 1, 

 figs. 1, 2), is covered throughout by a thin pellicle in which no sutures 

 are as yet visible. No part of an ancestral skeleton has been trans- 

 ferred to this distal and posterior daughter cell in the process of divi- 

 sion and it is apparently in the first stages of forming an entire new 

 skeleton, in the same fashion as a new one is formed from the delicate 

 peripheral pellicle secreted about the naked plasma in Gonyaulax 

 polyedra or in G. polygramma where the whole skeleton has been shed 

 by ecdysis or on the schizonts emerging from the mother theca in 

 Pyrophacus. There is then in this species no transmission of ancestral 

 skeletal parts during the process of fission which results in chain forma- 

 tion. 



