440 Illinois State Laboratory of Natural History. 

 EXPLANATION OF PLATE. 



ABBREVIATIONS. 



A., anterior pole. p. sh., outer or primary sheath 



c v., contractile vacuole. P. posterior pole. 



chr.. chromatophore. p., outer pellicle of protoplasm. 



/., flagellum. pr., knob-shaped mass of protoplasm 



m., matrix. pyr., pyrenoid. 



«., nucleus. s. sh., secondary sheath. 



ncl., nucleolus. st., stigma. 



Plate XXXVIII. * 



Fig. 1. Platydorina caudata, face view of 32-cell colony. X 5o0. 

 Fig. 2. Face view of 16-cell colony, y 628. 

 Fig. 3. Edge view of 32-cell colony. X 350. 

 Fig. 4. Lateral view of one of the marginal cells. X 1400. 

 Fig. 5, a — e. Outline of the posterior ends of several deformed colonies. 

 X 280. 



* Figures drawn by C. A. Kofoid and inked by Miss L. M. Hart. 



