56 



THE INVERTEBRATA 



Order VOLVOCINA 



Phytomastigina which have usually a flask-shaped, green chromato- 

 phore, with one or more pyrenoids, but are sometimes colourless, 

 though never holozoic; form starch reserves, even when colourless; 

 have no gullet or transverse groove ; possess usually a cellulose cuticle 

 and often haematochrome; and regularly undergo syngamy. 



Of all the Mastigophora, the members of this order most closely 

 resemble the typical plants. 



Fig. 41. 



Fig. 41. Noctiluca, x 65. A, Ordinaiy individual. B, Spore formation. 

 C, A spore. After various authors, with modifications, fl. flagellum; nu. 

 nucleus; ten. tentacle; tth. tooth. 



Fig. 42. Haematococcus lacustris, x 475. After West. A-C, Individuals in 

 ordinary phase, showing strands of protoplasm from body to cuticle. D-F, 

 Successive stages in fission. G, H, Individuals in resting phase. 



Chlamydomonas (Figs. 23, 25). Typical solitary members of the 

 order, with two flagella ; an eye-spot ; a close-fitting cellulose cuticle ; 

 and one pyrenoid. The various species exhibit isogamy, anisogamy, 

 and intermediate conditions (see p. 31). In fresh waters. 



Polytoma (Fig. 24). A colourless Chlamydomonas', retaining the 

 eye-spot (usually) and the habit of starch formation; but with the 



