No. 13. — Reports of the Scientific Results of the Expedition to the 

 Eastern Tropical Pacific, in charge of Alexander Agassiz, hy the 

 U. S. Fish Cominission Steamer "Albatross" from October, 

 1904, to March, 1905, Lieut. Commander L. M. Garrett. 

 U. S. N., commanding. 



XX. 



Mutations in Ceratium. By Charles Atwood Kofoid. 



CONTENTS. 



Normal schizogony in Ceratium 

 Division of ancestral skeleton 

 Formation of new skeletal 



parts 



Similarity of normal schizonts 



in ciiain 



The genus Ceratium . . . 

 Tripoceratium, subgen. nov. 

 Macroceratium, subgen. nov 

 Biceratium Vanhoffen 

 Amphiceratium VanhoflFen 

 Poroceratium Vanhoffen . 

 The mutation of Ceratium tripos 



to C. californiense 

 ' Chronology and nomenclature 



of skeletal parts of chain 

 Genuineness of the chain 

 Completeness of the chain 

 Evidence of mutation . . 

 Progressive perfection of 



mutant 



Significance of autotomy and 



213 

 214 



214 



the 



215 

 217 

 218 

 218 

 218 

 219 

 219 



220 



220 

 221 

 22.3 

 224 



225 



resolution of the C. iripos 



skeleton 



The mutation between Ceratium 



californiense and C. ostenfeldi 



Evidences of genuineness and 



completeness 228 



Earlier observations on mutations 

 in Protista . . . , 

 Mutations in Diatoms , 

 Mutations in Desmids . 

 Mutations in Ciliates 

 Mutations in Ceratium 

 Significance of the phenomenon 

 Unknown factors . , 

 Seasonal polymorphism (G 



and Lohmann) ... 

 Gamete hypothesis ... 

 Degeneration or atavism 



pothesis 



Mutation hypothesis . . 



Bibliography 



Explanation of Plates 



hy 



226 



227 



229 

 229 

 232 

 232 

 233 

 235 

 236 



237 

 244 



245 



247 

 253 



Normal Schizogony in Ceratium. 



Throughout the genus Ceratium asexual reproduction occurs, in so 

 far as is known, exclusively by schizogony. Multiple spore formation 

 such as is seen in some other genera of diuoflagellates, as for example 



