1893.J MICROSCOPICAL JoURXAL. 183 



and its poseiMc utilitarian puriKise. Hut there areoertain func- 

 tions oftlie contractile visicl<' whic'li do not call for even the 

 " scit iitiiio use of the imaj^ination," as they may he demonstrated 

 if not at all times at least occasionally, and sufficiently well to 

 leave no douht ; and if not in all mieroscopie animals of the 

 hnver classes, at least in enough to warrant trustworthy conclu- 

 sions. 



If we examine certain of the naked, fresh-water Rhizopods, 

 Actinophi-ys sol for instance, or ActinosjilifHrium eirhhornii, there 

 will not long be any doubt as to the manner in wliich the con- 

 tractile vesicles discharge their contents, nor where. 



In these common, soft-ljodied creatures of the ooze, the con- 

 tractile vesicles rise slowly from the suj-face of the ectoplasm as 

 gradually enlarging hemis})hcrical protuberances. Without 

 warning they collajise and, under a moderately high magnify- 

 ing ]iower, the point at which they disappearseems to sink into 

 the body with such violence that the shock usually jars the en- 

 tire animal, and informs the observer when the contraction has 

 been accomjtlished, although the vacuole may V)e on the oppo- 

 site side of the Rhizopod and not distinctly visible. With 

 greater amplification, in my own case with the use of a homo- 

 geneous immersion i N. A. 1.43, and an oil-immersion 1-12, N. 

 A 1.40, imjiortant details may be noted. These are similar in 

 both Rhizopods, being rather more conspicuous and more eas- 

 ily seen in Aclhidsplurrbim eichhornii than in Adinophryssol, sim- 

 ply on account of its greater size. 



When the vesicle has reached its point of greatest expansion, 

 that is, when the diastole is complete, its surface is entirely 

 smooth, but as it contracts the whole becomes studded with 

 projections which are hollow, nipple-like and of unequal lengths, 

 each villus communicating directly with the cavity of the con- 

 tractile organ and being filled with the same contents. These 

 projections are forced out from the general surface of the vesicle 

 with violence, their free extremities becoming suddenly rounded 

 as if through quickly applied pressure from within, the entire 

 performance reminding the observer of the childish sport of 

 blowing into a kid glove to see the inflated fingers leap up. 

 The quickly produced appendages are either slowly withdrawn 

 and so made to disajipear, or they are smoothed out by ihe 

 gradual dilatation of the swelling vesicle. 



