FLAGELLATA 1 I 9 



un increased toleration and resistance from one generation or 

 cycle to another. 



As we noted above (p. 40), the study of tlie Flagellates has 

 been largely in the hands of botanists. After the work of Biitschli 

 in Bronn's Thier-Picich , Klebs ^ took up their study; and the prin- 

 cipal monographs during the last decade have appeared in Engler 

 and Prantl's Pjianzenfaviilien, where Senn "- treats the Flagellates 

 generally, AVille ^ the Yolvocaceae, and Schiltt the " Peridiniales " 

 or DinoHagellata ; ■* while only the Cystoflagellata, with but two 

 genera, have been left to the undisputed sway of the zoologists.'^ 



Among this group the majority are saprophytes, found in 

 water containing putrefying matter or bacteria. The forms so 

 carefully studied by Dallinger and Drysdale belong to the genera 

 Bodo, Cercornonas, Tetramitiis, Monas, and DaUingcrid. Many 

 others are parasites in the blood or internal cavities of higher 

 animals, some apparently harmless, such as Trichomonas vaginalis, 

 parasitic in man, others of singular malignity. Costia necatrix, 

 infesting the epithelial scales of fresh-water fish, often devastates 

 hatcheries. The genus Trypanosoma, Gruby, contributes a 

 number of parasites, giving rise to deadly disease in man and 

 beast.'' T. leivisii is common in Eodents, but is relatively harm- 

 less, T. evansii is the cause of the Surra disease of Euminants 

 in India, and is apparently communicated by the bites of " large 

 brown flies " (almost certainly Breeze Flies or Tabanidae, Vol. YI. 

 p. 48 1). T. hrucei, transferred to cattle by the Tsetse Fly, Glossina 

 ynorsitaiis (see Yol. YI. Fig. 244, p. 513) in Equatorial Africa, is 

 the cause of the deadly ISTagana disease, which renders whole 

 tracts of country impassable to ox or horse. Other Trypanosomic 

 diseases of animals are, in Algeria and the Punjab, " dourine," 

 infecting horses and dogs ; in South America, Mai de Caderas 

 (falling-sickness), an epidemic paralysis of cattle. During the 

 printing of this book, much additional knowledge has been gained 

 on this genus and the diseases it engenders. • The Trypanosomic 



1 In Z. wiss. Zool. Iv. 1893, p. 353. 2 | t^^^^ ^,^^ -, .,^ ^c,qq 



3 In the Chlorophyccae, 1. Teil, Abt. 2, 1897. ■• 1. Teil, Abt. 1. h, 1896. 



* Besides tlie above, Daiigeard, in various papers in his periodical Le Bofaniste, 

 has treated of most of the groups, and Raoul France has monographed tlie P0I3'- 

 tomeae in the Jahrb. wiss. But. xxvi. 1894, p. 29.5, and Dill the genus Chlainii 

 domonas, etc., its closest allies, in op. cit. .xxviii. 1895, p. 323. 



•* For a detailed abstract of our knowledge of Trypanosoma and its allies up to 

 Feb. 1, 1906, see Woodcock, " Tiie HaenioHagellates," in Quart. Journ. Micr. Sci. 

 1. 1906, p. 151. 



