92 WISCONSIN PHYTOPLANKTON 



Many of the empty Dinobryon receptacles in these three connecting 

 lakes were filled with a minute green organism. These had cilia, even 

 when in the receptacle, and on the slightest crushing of the receptacle 

 began swimming around outside of it. Since cilia are constantly pres- 

 ent the alga is a Chlamydomonas and not one of the Palmellaceae col- 

 lected at the time of reproduction. 



Family CARTERIACEAE. 



Cells normally motile and with four cilia of equal length at the an- 

 terior end. Solitary, or in coenobia containing a definite number of 

 cells. Cell shape spherical, ovoid, ellipsoid, cardioid, pyriform, or 

 lenticular. Cells enclosed by a definite wall, and with or without a 

 cup-shaped to lenticular chloroplast that is with or without pyrenoids. 

 Eyespot generally present, conspicuous, and at the anterior end of the 

 cell. Cells frequently with contractile vacuoles at the base of the 

 cilia. Palmella stages known in the solitary members of the family. 



Asexual reproduction by the division of cell contents into 2-16 tetra- 

 ciliate zoospores or into autocolonies. 



Sexual reproduction isogamous, by a fusion of tetraciliate zoogametes. 



CARTERIA Diesing 1866. 



Cells solitary, generally motile throughout the vegetative phases of 

 the life cycle. Spherical, ovoid, ellipsoid, or cardioid in shape; with 

 four cilia of equal length at the anterior end. Cell contents consisting 

 of a single cup-shaped chloroplast that contains a pyrenoid; one eye- 

 spot; and two contractile vacuoles at the base of the cilia. Palmella 

 stages containing an indefinite number of cells are found at times. 



Asexual reproduction by division of cell contents to form 2-8 tetra- 

 ciliate zoospores. 



Sexual reproduction by the division of cell contents to form 4-64 

 tetraciliate zoogametes that fuse in pairs to form zygotes with smooth 

 or sculptured walls. 



KEY TO THE SPECIES. 



Cells ellipsoid C. KLEBSII 



Cells cardioid C. COBDIFORMIS 



CARTERIA CORDIFORMIS (Carter) Diesing. PI. 16, Fig. 1. 



Sitzbr. d. k. Ak. d. Wiss. Wien, Mat.-Naturw. Kl. 52 1 : 356. 1866; Dill, Jahrb. f. 

 wlss. Bot. 28: 353, pi. 5, figs. 42-44. 1895. 



Cells cardioid in shape with four cilia at the base of the apical de- 

 pression. Chloroplast cup-shaped, fairly massive, with a single pyre- 



