THE MAST1GOPHORA 179 



There is usually a single large green chloroplast enclosing one 

 or more pyrenoids, and the product of metabolism is starch. The 

 vacuole-system consists, as a general rule, of two alternately con- 

 tracting vacuoles. There is a red stigma at or near the flagellar 

 basis. There are never less than two equal flagella, rarely four as 

 in Carter ict and Pyramidomonas. 



The Phytoflagellata are freshwater in habit. 



Among the organisms which are closely related to the Phytoflagellata, 

 but which are regarded in this volume as being just over the border-line 

 between the animal and vegetable kingdoms, we may include the families 

 Pleurococcaceae, Hydrodictyaceae, Protococcaceae, and Palmellaceae. The 

 genera Pleurococcus, Menegh., and Trochiscia, Kiitzing, belonging to the 

 Pleurococcaceae, have a more definite cell -wall and a more pronounced 



FIG. 7. 



1, Salpingoeca fiisiformis, Kent ; one of the Craspedomonadina. The protoplasmic body is 

 drawn together within the goblet-shaped cell, and divided into numerous spores, x 1500. 

 2, escape of the spores of the same as monomastigote swarm-spores. 3, Codosiga umbellata, 

 Tatem ; one of the Craspedomonadina. Adult colony formed by dichotomous growth, x 625. 



4, a single zooid of the same, x 1250. a, nucleus ; b, contractile vacuole ; c, the collar. 



5, Hexamitus inflates, Duj. ; one of the Polymastigina, x 650. Normal adult showing (a) nucleus 

 and (b) contractile vacuole. 6, 7, Salpingoeca urceolata, Kent; one of the Craspedomonadina. 

 ti, with collar extended ; 7, with collar retracted within the stalked cupule. 8, Polytoma uvella, 

 Mull. ; one of the Chlamydomonadina, x 800 ; a, nucleur. : b, contractile vacuoles. 9, Lophomonas 

 blattarum, Stein ; one of the Polymastigina. 10, Bodo lens ; one of the Heteromastigoda, x 800 ; 



a, nucleus ; b, contractile vacuole ; the wavy filament is a flagellum, the straight one is the 

 gubernaculum. 11, Tetramitus suloatus, Duj. ; one of the Polymastigina, x 430; n, nucleus; 



b, contractile vacuoles. 12, Anthophysa vegetans, O. F. M. ; one of the Paramastigoda, x 300. 

 A typical, erect, shortly-branching colony stock with four terminal monad clusters. 13, monad 

 fluster in same optical' section (x 800), showing the relation of the individual monads to the 

 stem (a). 14, Tetrn.mitvs rout rat us, Perty, x 1000 ; a, nucleus ; b, contractile vacuole. 15, 

 I'roterospongia haeckeli, Kent ; one of the Phalansteriina, x 800. A social colony of about forty 

 flagellate zooids. a, nucleus ; b, contractile vacuole ; c, amoebiform zooid sunk within the 

 common test ; d, similar zooid multiplying by transverse fission ; e, normal zooids with their 

 collars retracted ; /, hyaline mucilaginous common test or zoothecium ; g, individual contracted 

 nnd dividing into minute flagellate spores (microgametes), comparable to the spermatozoa of a 

 sponge. (After Lankester and various authors.) 



vegetative phase of life than Sphaerella, but in other respects are closely 

 related to it. The genus Hydrodictyon, Roth, forms a net-like coenobium 

 which floats at the surface of the water, and Pediastrum, Meyen, which 

 is also placed in the family Hydrodictyaceae, a flat plate-like coenobium 

 of cells that is protected by a thick and ornamented cell- wall. Among 

 the Protococcaceae such genera as Botryococcus, Kiitzing ; Tetracoccus, 

 West ; Ineffigiata, West, are probably closely related to some ancestral 

 form allied to Sphaerella ; but in some of the other genera, such as 

 Selenastrum, Reinsch ; Ankistrodesmus, Corda ; Dadylococcus, Nageli, in 

 which the cells are elongated and spindle-shaped ; and in Archerina, 

 Lankester l ; and Chodatella, Lemmerniann, in which the cell-walls are 

 provided witli long, stiff, bristle-like processes, there is a more pronounced 

 diversion from the Chlamydomonadine ancestry. 



The family Palmellaceae has diverged from the same ancestry by the 

 development of a conspicuous envelope of mucilage, but it contains some 



1 The genera Golenkinia, Chodat, Richteridla, Lemmermann, and Phytheliiis, 

 JFrenzel, are probably the same as Archerina (see p. 33). 



