348 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



and for them phosphates are especially attractive. The hyphae of Fungi 

 respond in general to the same substances as Bacteria and Flagellatae, and 

 their positive and negative chemotropism has the character of a tropic 

 movement. The different grades of repulsion exerted by weak acids on 

 various Flagellatae as well as on fungal hyphae and on Bacteria are of 

 similar character l . It remains, however, to be seen whether all Flagellatae 

 are capable of a tropic reaction, and to what extent the osmotropic reactions 2 , 

 which are as well developed in these organisms as in Bacteria, are carried 

 out in a tropic or a phobic manner. It may be mentioned that the Infusoria 3 

 are usually not chemotactically stimulated by the substances mentioned, 

 but that certain species at least are capable of a positive phobotactic 

 response towards dilute acids including carbonicacid, and of a negative 

 one away from more concentrated solutions. 



Myxomycetes. According to Stahl 4 the plasmodia show a positively 

 chemotactic amoeboid movement towards an extract of tan, and Stange 5 

 has found that various substances act as stimuli. Stange has also shown 

 that the zoospores of Aethalium and Chondrioderma are attracted by 

 various substances, more especially by lactic, butyric, and malic acids. 

 Concentrated solutions, or ones with a strong acid reaction, exert a repulsive 

 action upon the zoospores as well as upon the plasmodia. It may inciden- 

 tally be mentioned that the amoeboid leucocytes of animals are chemo- 

 tactically stimulated by a variety of substances, and that by reactions of 

 this kind various definite and physiologically important movements may 

 be produced within the body 6 . 



THE USES OF CHEMOTAXIS AND ITS EXCITANTS. 



By means of their chemotactic irritability organisms may be attracted 

 to regions where food-material is abundant, or where their function is 



According to Rothert (1. c., p. 375) only the second zoospore stage responds chemotactically. The 

 substances which attract the zoospores of Chytridiaceae are not known. Cf. Pfeffer, 1. c., 1888, p. 643. 

 According to \V. Benecke (Jahrb. f. wiss. Bot., 1900, Bd. xxxv, p. 554), Diatomaceae are capable of 

 both chemotactic and aerotactic responses. 



1 Pfeffer, 1. c., 1888, p. 625. According to Carrey (American Journal of Physiology, 1900, 

 Vol. in, p. 291), Chilomonas exhibits a normal tactic reaction to dilute acids, and a phobic one to 

 concentrated acids and other substances. 



2 Cf. Massart, Archives de Biologic, 1889, T. IX, p. 531 ; Bull, de 1'Acad. royale de Belgique, 

 1891, 3 e sen, T. xxn, p. 148. 



3 Jennings, Journal of Physiology, 1897, Vol. XXI, p. 320; American Journal of Physiology, 

 1900, Vol. in. 



4 Stahl, Bot. Ztg., 1884, p. 155. Olive (Proc. of the Boston Soc. of Natural History, 1902, 

 Vol. xxx, p. 463) could detect no chemotaxis in Acraseae. 



5 Stange, Bot. Ztg., 1890, p. 155. 



* Cf. Verwora, Allgem. Physiologic, 3. Aufl., 1901, p 451. 



