I'UOTOZOA 



43 



the other lying in a groove which passes around the body trans- 

 versely. There is almost always a shell of cellulose, often more 

 or less ornamented by various kinds of projections (Fig. 25). 

 Chlorophyll or some similar pigment is generally present, as 

 well as a nucleus or nuclei, and a contractile vacuole. The 

 method of nutrition in some cases is that of plants, in others, 

 that of animals, and they reproduce by division. This order is 

 largely marine. 



Fig. 25. 1, Ceratium tripos, a Dinoflagellate; 2, Noctiluca vnlia>is,\\ Cystoflagellate ; 

 3,Leptodiscus medusoides ,a Cystoflagellate, in section, (i.from Biitschli's Protozoa; 

 2, chiefly after Cienkowski ; 3, after Hertwig, from Delage and Herouard's Traite de 

 Zoologie.) 



Order 4. Cystoflagellata 



The Cystoflagellata (Gr. kihttis, a bag) are represented by 

 only two genera, Noctiluca and Leptodiscus, both marine, and 

 having a cystlike structure. Noctiluca (Fig. 25) is more or loss 

 spherical, bounded by a thin cuticula ; the protoplasm is greatly 

 vacuolated, appearing as a granular mass surrounding the nu- 

 cleus, with a network of fine threads extending to the periphery. 

 There is a mouth with a short flagellum, and near by a second 

 flagellum much larger than the first, known as the tentacle, 

 which is marked by transverse bands. Noctiluca possesses the 



