Dr. C. A. Kofoid on Platydorina. 057 



S/jecies. 



QONICM. 



I Cells 4 aoeiale {Dyi\.)A 



I Cells Hi pectorale, Miill. 



SrKI'UANOSPU^BA. 



Represented by a single species, characterized aa 

 follows : — Cells 4 or 8, ovoid or spindle-shaped, 

 with numerous processes pluvialU, Cohn.* 



Pandouixa. 



Represented by a sin^'le species, characterized aa 

 follows : — Cells 16 or 32, crowded, each with 

 a single chromatophore and pyrenoid morum, Bory. 



EUDORIMA. 



Represented by a single species, characterized att 

 follows: — Cells 32, IG, or 64, similar, not 

 crowded together ; common outer membrane 

 without marked concentric structure elegans, Ehrb. 



Platydorixa. 



Represented by a single species, characterized as 

 follows : — Cells 16 or 32, arranged in a horse- 

 shoe-shaped plate, those of the two faces inter- 

 calated. Posterior end with 3 or 5 tails .... caudata, Kofoid. 



Pleodorixa. 



r Cells 64 or 128 ; gonidial cells about two to three 

 I times the diameter of vegetative cells, which 



I con-.titute about one half the total number 



and lie in anterior hemisphere californica, Shaw. 



Cells 32, rarrly 16 or 64 ; gonidial cells not more 



than twice the diameter of the vegetative 



cells, which constitute the anterior quartet. . tlltnoisensis, Kofoid. 



VOLVOX. 



''Cells about 10,000 (minimum loOO, maximum 

 22,000), angular, with stout connecting 

 protoplasmic processe-t into which the chro- 

 matophore may enter. Diameter of colony 

 about 700 fi (minimum 400, maximum 



1200) ; diameter of cell-bodv 3 o /i globator, L. 



Cells 500-1000 (minimum 200, maximum 4400), 

 rounded, with slender connecting protoplas- 

 mic processe.s into which the chromatophore 

 does not enter. Dimnetc-r of colony 170- 

 8oO ft. ; diameter of cell-body 5-8 n aureuM, Ehrb. 



Universitv of Illinois, 



Urbana, 111., U.S.A., 



Dec. o, 1899. 



Ann. ,f; M^t;/. A'. Hist. Ser. 7. Vol. vi. 37 



