326 M. N. Lieberkuhn on the Anatomy of the Infusoria, 



one point. Tliis completes the systole. The diastole then re- 

 commences. If we examine the animal at the moment when the 

 reservoir has again attained half its greatest diameter^ we find a 

 totally different appearance from that at the corresponding epoch 

 of the systole. The vessels are not expanded now in the form 

 of a spindle, but of a funnel, with the base of the funnel in 

 the contractile vesicle, and the point prolonged out into the 

 vessel. This is the form which Ehrenberg has figured in Para- 

 meciwn Aurelia, only omitting the further prolongations of the 

 vessels ; Von Siebold rejects Ehrenberg's figure, and recognizes 

 Dujardin's ; but both are really correct, only representing 

 different instants ; Dujardin gives a stage of the systole^ Ehren- 

 berg of the diastole. 



The more the contractile vesicle now expands, the more is 

 the depth of the funnel decreased, and its diameter proportion- 

 ately increased ; or, in other words, the vessel expands only at 

 its embouchure, and the depth of the expanded part decreases in 

 proportion with the advance of the diastole. In opake Bursarice, 

 we see at this time only the contractile vesicle produced out in 

 various directions into short funnel-shaped processes. By 

 degrees these processes entirely disappear, the contractile vesicle 

 having expanded to its original volume. We now see again 

 how, from the fully expanded contractile vesicle, the whole of 

 the vessels run out in the cortical layer, in all directions, as 

 slender streaks ; in opake specimens, only the contractile reser- 

 voir is visible. 



The processes above described are those usually observed when 

 a suitable specimen is placed so that it cannot move, or only 

 move very little, upon the slider. If, however, a Bursaria is 

 compressed somewhat more with the covering-glass, or if the 

 water on the slider is almost all evaporated, some other peculiar 

 phsenomena present themselves, not only in the contractile 

 vesicle, but in the vessels. The last diastole coming, perfectly 

 to rest, and nothing unusual being observed, except that the 

 reservoir is more elongated, with the systole appear suddenly 

 two contractile vesicles instead of one ; that is, a portion of the 

 surrounding substance makes its way across the middle of the 

 contractile vesicle while it is contracting, and thus divides it 

 into two parts. Each of these two new reservoirs has its own 

 systole and diastole. In most cases their contractions do not 

 occur at the same moment. Each is in connexion with those 

 vessels which opened into it before the separation. The vessels 

 exhibit the same play as if there were but one uninjured con- 

 tractile vesicle. Sometimes the two reservoirs reunite into a 

 single one. I saw this happen during a diastole which oc- 

 curred exactly simultaneously in both ; they advanced near 



