MORPHOLOGY 91 



brownish red dot or short rod, embedded in the cortical layer of the 

 cytoplasm. The color of the stigma is due to the presence of droplets 

 of haematochrome in a cytoplasmic network. The stigma is incapable 

 of division and a new one is formed de novo at the time of cell divi- 

 sion. In many species, the stigma possesses no accessory parts, but, 

 according to Mast (1928), the pigment mass in Chlamydomonas, 

 Pandorina, Eudorina, Euglena, Trachelomonas, etc., is in cup-form, 

 the concavity being deeper in the colonial than in solitary forms. 

 There is a colorless mass in the concavity, which appears to function 

 as a lens. In certain dinoflagellates, there is an ocellus (Fig. 127, c, d, 

 q, h) which is composed of amyloid lens and a dark pigment mass 

 (melanosome) that is sometimes capable of amoeboid change of form. 

 The stigma is, in general, regarded as an organella for the perception 

 of light intensity. Mast (192G) considers that the stigma in the Vol- 

 vocidae is an organella which determines the direction of the move- 

 ment. 



References 



Alexeieff, A.: (1928) Sur la question des mitochondries et de l'ap- 

 pareil de Golgi chez les protistes. Arch. Protist., 60:269. 



(1929) Nouvelles observations sur les chondriosomes chez les 



protozoaires. Ibid., 65:45. 



Arcichovskij, , V. : (1905) Ueber das Zoopurpurin, ein neues Pig- 

 ment der Protozoa (Blcpharisma lateritium). Arch. Protist., 6: 

 227. 



Beers, C. D.: (1946) Tillina magna: micronuclear number, etc. 

 Biol. Bull., 91:256. 



Belar, K.: (1926) Der Formwechsel der Protistenkerne. Ergebn. u. 

 Fortschr. Zool., 6:235. 



Bresslau, E. and Scremin, L. : (1924) Die Kerne der Trypano- 

 somen und ihre Verhalten zur Nuclealreaktion. Arch. Protist., 

 48:509. 



Brodsky, A.: (1924) Die Trichocysten der Infusorien. Arch. russ. 

 Protist., 3:23. 



Brown, H. P.: (1945) On the structure and mechanics of the proto- 

 zoan flagellum. Ohio J. Sc, 45:247. 



Brown 1 , V. E. : (1930) The Golgi apparatus of Amoeba proteus. Biol. 

 Bull., 59:240. 



(1930a) The Golgi apparatus of Pyrsonympha and Dine- 



nympha. Arch. Protist., 71:453. 



(1930b) The neuromotor apparatus of Paramecium. Arch. 



zool. exper. g£n., 70:469. 



Burt, R. L. : (1940) Specific analysis of the genus Colpoda with spe- 

 cial reference to the standardization of experimental material. 

 Tr. Am. Micr. Soc, 59:414. 



Chadefaud, M.: (1938) Nouvelles recherches sur l'anatomie com- 

 pare des Eugleniens: les Peranemines. Rev. Algol., 11:189. 



