Kopoid. — Mutations in Ceratium. 



EXPLANATION PLATES. 



PLATE 1. 



Fig. 1. Ventral view of mutating chain of Ceratium. Posterior cell (IV 3 ) is 

 Ceratium tripos, the other three (I g , II 3 , and III 3 ) are C. califomiense. 

 Aj, A 2 , and A 3 are anterior, and P 1( P 2 , and P 3 posterior skeletal moie- 

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

 spectively. A heavier suture marks the fission line (/. /.). The apical 

 pore {ap. p.) is at the anterior end of the 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. The chain channel (ch. ch.) lies to the rear of 

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

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

 lar plates (V'-i"), girdle plates (g. pi.), postcingular plates (V "-&'"), 

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



