KoFoiD. — Mutations in Ceratium. 



EXPLANATION PLATES. 



PLATE 1. 



Fig. 1. Ventral view of mutating chain of Ceratium. Posterior cell (IV3) is 

 Ceratium tripos, tiie otlier tliree (Ig, II3, and III3) are C. californiense. 

 Aj, A2, and A, are anterior, and P^, P,, and P3 posterior slieietal moie- 

 ties formed on tlie cells of the first, second, and third generations re- 

 spectively. A lieavier suture marks the fission line (/. /.). Tlie apical 

 pore {ap. p.) is at the anterior end of tlie apical horn, the flagellar pore 

 {fl. p.) at the proximal end of the girdle {g.), and the attachment area 

 {att. a.) at its distal end. Tlie chain channel (ch. ch.) lies to the rear of 

 this area along the side of tlie ventral "plate" (v. p.). Tlie skeleton 

 consists of the following plates : Apical series of plates (l'-4'), precingu- 

 lar plates (l"-4"), girdle plates (7. />/.), postcingular plates (r"-5"'), 

 antapical plates (\""-2""), and the so-called " ventral plate." X 540. 



