298 LOCOMOTORY AND PROTOPLASMIC MOVEMENTS 



however, be no more remarkable than the formation of a non-contractile one \ and 

 this might still occur even though the vacuole always reappeared at the same spot. 

 A localization of the vacuole merely involves a localized production of the conditions 

 for its formation. The latter may or may not involve the coalescence of preformed 

 droplets, but in any case the degree of independence and of differentiation attained by 

 pulsating vacuoles is not in all cases certain 2 . 



External influences. The frequency attains a maximum at a certain optimal 

 temperature, and in general the responses resemble those for other forms of vital 

 activity 3 , although the vacuoles appear to have a higher resistant power. Thus, 

 according to Klebs, mechanical agencies, high temperatures, and strychnine stop the 

 general protoplasmic movements before the pulsation of the vacuoles ceases, and the 

 latter is the first to begin on returning to normal conditions. Indeed, according to 

 Klebs 4 , irregular slow pulsations may continue for a time after the general mass of 

 the cytoplasm has been killed by heat or disorganized by pressure. Evidently, 

 therefore, the pulsation is independent of the nucleus, and it may also continue for 

 a time in non-nucleated masses of living cytoplasm. Rossbach found that induction- 

 shocks as well as certain alkaloids stopped the ciliary movement and locomotion of 

 Infusoria before the pulsation of the vacuoles had ceased. Dodel 5 , however, found 

 that the vacuolar pulsation and ciliary movement of the zoospores of Ulothrix ceased 

 simultaneously, and that in other zoospores the cilia continued to move after pulsation 

 had ceased, so that specific differences appear to occur according to the organism 

 examined 6 . 



Various agencies may cause an enlargement of the vacuole, and this change is in 

 some cases reversible and extremely pronounced. When thus swollen the vacuoles 

 may pulsate little or not at all. Klebs found that this effect was produced in the case 

 of Euglena by various neutral salts which, however, appear to be less effective in their 

 action upon Infusoria. Rossbach was indeed unable to detect any action at all upon 

 them, but Massart has shown that it takes place at a particular concentration 7 . High 

 concentrations naturally produce a plasmolytic contraction, and in some cases a 

 complete collapse of the vacuoles 8 . Rossbach found that alkaloids and alkalies 

 caused an enlargement of the vacuoles of Infusoria, but Klebs was unable 'to detect 

 any distension when Euglena was exposed to the action of strychnine. Both Klebs 

 and Massart have, however, observed a gradual accommodation of the vacuoles to 

 concentrated solutions. 



1 Pfeffer, Plasmahaut u. Vacuolen, 1890, p. 223. Biitschli and Rhumbler also consider that the 

 vacnoles are formed anew after each complete pulsation. 



2 Cf. Pfeffer, I.e., 1890, p. 223. 



3 Biitschli, Protozoen, 1880-8, pp. 715, 1454 ; Klebs, Unters. a. d. hot. Inst. zu Tubingen, 1883, 

 Bd. i, p. 248. 



4 Rossbach, Die rhythmischen Bewegungserscheinungen d. einfachsten Organismen, 1872, p. 56. 

 See also Biitschli, 1. c., p. 1455. 



5 Dodel, Bot. Ztg., 1876, p. 185. 



6 Cienkowski, Bot. Ztg., 1865, p. 23; Strasbnrger, Ueber Zellbildnng u. Zelltheilung, 1875, 

 P- J 57- 



7 Massart, Archive de Biologic, 1889, T- IX > P- 55- 



8 Cohn, Nova Acta Acad. Caesar. Leopold., 1854, Bd. xxiv, i, p. 194; Klebs, I.e. ; Massart, I.e. 



