189;l] MICKOSCOPICAI. .K X'JLX A I.. Si 



mimite. Anything that reduces tlic vitality of the organism will 

 reduce the nuiiiher of pulsations in a j^iven time. Whether there 

 is any connection l)etwcen the two vesicles I am unahle to state. 

 There was no visilile connection. Death takes place, as a rule, 

 ilurin<; a diastole ; the \esicle often increasing to such size as to 

 rupture the cell-wall. I made the most careful observations to 

 find Stein's openings in the cell-wall for the ejection of "•water." 

 hut could not find any, neither one nor several. I found indica- 

 tions of a " tube." It was temporary, however, forming a part 

 of the vesicle and extending onlv to the cell-wall. More often 

 this projection was absent. In looking vertically ilownward upon 

 the ciliated cell-wall the points of attachment of the cilia gave 

 the appearance of black dots. These might be mistaken for open- 

 ings, especially when just o\er the contractile vesicle and after its 

 contraction because of the sinking of the cell-wall. I am certain 

 that no currents due to any ejection of li(juids are noticeable. 



I shall now give a more complete description of the contrac- 

 tile vesicle. It is a temporary cavity formed in the ectosarc, with 

 canals leading to it. These canals are much enlarged where 

 they join the main vesicle. These expansions, which are gen- 

 erally spherical, I will call secondary vesicles or Vorhofe. The 

 canals (conducting canals) are long and slender and always lo- 

 cated in the ectosarc. and have no apparent connection with each 

 other. Their number for each vesicle varies from four to seven 

 or eight. Sometimes neither the canals nor Vorhofe are visible. 

 The vesicle, Vorhofe and canals are not lined by a membrane. 

 Their position is not absolutely fixed. \\'hether the slight shift- 

 ing is due to a change in position of the vesicle or to the entire 

 protoplasmic mass I am unable to state. I have divided a com- 

 plete pulsation of a vesicle into three periods: ], the s\stole of 

 the vesicle ; 2. tlie rest period of the \esicle ; 3. the diastole of the 

 vesicle. 



To speak of the movements of the vesicle is misleading, be- 

 cause there is no such organ or structure as a contractingvesicle. 

 It would be more correct to speak of the movements or contrac- 

 tions of the cell protoplasm, causing the appearance and disap- 

 pearance of the vesicle. But for convenience sake we shall con- 

 tinue to speak of the vesicle as an organ. The following will 

 assist in giving an idea of a complete pulsation of the vesicle : 



I. Systole of Vesicle : Average Time, ^ Second. 



Movements. — Vesicle contracts suddenly. 

 \'orhofe expands. 

 Canals expand slightly. 



Position, — Vesicle contracts eccentrically towards exterior. 

 Vorhofe remains in position. 

 Canals remain in ]:)nsition. 



