346 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



It is not yet certain whether the antherozoids of Fucaceae adhere to 

 the ovum simply as the result of a contact-stimulus, as Bordet supposes, or 

 whether chemotactic influences come into play l . Further, it is questionable 

 whether the sperms of Chara experience any chemotactic attraction, and 

 the latter does not seem to be responsible for the conjugation of the zoospores 

 of Chlamydomonas or of Ulothrix sonata 2 , which seems to be left to chance. 

 It is, however, hardly surprising that, as in the case of pollination, various 

 modes should be used to bring motile sexual cells together 3 . In all cases, 

 however, the ultimate fusion is determined by the properties of the proto- 

 plasts ; so that, although the sperms of other species may be attracted into 

 the archegonium and come into close contact with the ovum, no fusion 

 occurs. The special attraction exerted by malic acid and its salts as well 

 as their actual presence in the prothallus indicate their importance as agents 

 for inducing fertilization in Ferns 4 . 



Bacteria. Motile Bacteria show all grades of sensibility, and both the 

 chemotactic and osmotactic reactions are carried out in a phobotactic 

 manner. Very sensitive forms react positively to most substances, but the 

 less sensitive forms give little or no reaction when feebly stimulating sub- 

 stances are used 5 . Peptone and potassium salts are especially active, and 

 are responsible for the high attractive power of meat extract. Sodium 

 and calcium salts, asparagin and urea, are less active as stimuli, and while 

 glycerine appears to produce no attraction at all, oxygen appears to influence 

 all bacteria strongly. 



Bacterium termo G and Spirillum undula appear to be especially sensitive, 

 for a response is produced when the liquid in the capillary contains o-coi per 

 cent, of peptone, potassium chloride, or of meat-extract. Spirillum serpens, 

 S. volutans, Bacillus subtilis, and especially Spirillum Finkler- Prior, are 

 much less sensitive. Dextrin attracts Bacterium termo strongly, but 

 Spirillum undula very feebly 7 , while only a few bacteria are chemotactically 

 affected by ether 8 . Sulphuretted hydrogen attracts Chromatium Weissii 



1 Thuret, Ann. d. sci. nat, 1854, 4" sen, T. II, p. 17; Bordet, Bull, de 1'Acad. royale de 

 Belgique, 1894, 3 e ser., T. xxvil, p. 889; Farmer and Williams, Phil. Trans., 1898, Vol. cxc, 

 PP- 633, 643; Buller, Quarterly Journal of Microscopical Science, 1902, Vol. XLVI, p. 148. 



8 Pfeffer, 1. c., 1884, pp. 438, 441. 



3 Cf. Pfeffer, 1. c. 1884, p. 447. Chemotactic sensibility appears to be absent from the sperms 

 of Rana (Massart, Bull, de 1'Acad. royale de Belgique, 1888, 3" ser., T. xv, Nr. 5, und 1889, Nr. 8) 

 and of Echinodermata (Buller, Quarterly Journal of Microscopical Science, 1902, Vol. XLVI, p. 151), 

 but is shown by those of the rat (Otto Low, Sitzungsb. d. \Vien. Akad., 1902, Bd. CXI, Abth. iii, 

 p. 1 1 8). 



* Pfeffer, 1. c., p. 884 ; Buller, 1. c., 1900, p. 570. 



5 For details see Pfeffer, Unters. a. d. bot. Inst. zu Tubingen, iSSS, Bd. n, p. 582. 



c Pfeffer (1. c., p. 590) mentions what is included under the term 'Bacterium termo? 



7 Pfeffer, 1. c., p. 606. 



8 Rothert, Flora, 1901, p. 380. 



