Carteriese 



1(59 



close contact with the protoplast. This character, and the presence of only 

 two contractile vacuoles 1 situated at the anterior end of the cell close to the 

 base of the cilia, are the leading distinctions between the Volvocaceas and the 

 SphaBrellaceee. In the majority of forms the chloroplast contains only one 

 pyrenoid, although several normally occur in Chlamydomonas giganteus Dill 

 and Pleodorina illinoisensis Kofoid ; and Bachmann ('05) has occasionally 

 observed two or three pyrenoids in specimens of Chlamydomonas inhxrens. 



In the few forms included in the Carteriese (the Carteriacete of Pascher) 

 the cells are furnished with four cilia. 



Sub-fain. Carteriese. 



The Volvocacese may be subdivided as follows : 



A. Cells with four cilia ; unicellular or coenobic. 



B. Cells with two cilia. 

 a. Unicellular. 



*Cell-wall thin but distinct. Sub-fain. Chlamydomonadex. 



**Cell-wall firm and often thick, sometimes consisting of two loosely con- 

 nected halves. Sub-fain. Phacotese. 



b. 



Cells aggregated to form crenobia with very definite characters. 



Sub-fain. Volvocess. 



Sub-family CARTERIE/E. All the 

 equal cilia attached to the anterior 

 end of the cell. The principal genus 

 is Carteria, in which the cells are 

 spherical, ovoid or ellipsoid, and pro- 

 vided with a thin cell-wall. Near the 

 attachment of the cilia are two small 

 contractile vacuoles; and a conspicuous 

 pigment-spot is present, although its 

 position is variable. The chloroplast 

 is large and massive, hollowed out 

 anteriorly into the form of a basin or 

 cup, and is usually furnished with a 

 single conspicuous pyrenoid in its pos- 

 terior thicker part (fig. 98 A and B). 

 The presence of four cilia is the only 

 feature distinguishing this genus from 

 Chlamydomonas. In the formation 

 of zoogonidia the first division-plane 

 is longitudinal or slightly oblique. 

 In several species quadriciliated 

 isogametes are also known, which 



genera of this sub-family possess four 



Fig.98. A G, Carterin mW/is(Fresen.)Dill; 

 A and B, vegetative cells ( = zoogonidia) ; C, 

 four daughter-cells within old wall of mother- 

 cell; D, gametes; E, conjugating gametes; 

 F, zygote. H and /, Chlamydomonas Debary- 

 ana Gorosch. J and A', Chi. grandis Stein 

 ( = Chi. Kleinii Schrnidle). All x 475. cv, con- 

 tractile vacuoles; n, nucleus; p, pyrenoid; 

 zg, gamete; z, zygote. 



1 In Agloe there is an additional group of three contractile vacuoles at the posterior end of 

 the cell (vide Pascher, '12). 



