1893.] MICROSCOPICAL JOURNAL. 183 . 



and its possible utilitarian purpose. But there are certain func- 

 tions of the contractile vesicle which do not call for even the 

 " scientific use of the imagination," as they nia y be demonstrated 

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

 leave no doubt; and if not in all microscopic animals of the 

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

 sions. 



If we examine certain of the naked, fresh-water Rhizopod a, 

 Adinophrys sol for instance, or ActinospJixrium eichhornii, there 

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

 tractile vesicles discharge their contents, nor where. 



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

 tractile vesicles rise slowly from the surface of the ectoplasm as 

 gradually enlarging hemispherical protuberances. Without 

 warning they collapse and, under a moderately high magnify- 

 ing power, the point at which they disappear seems 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 accomplished, although the vacuole ma}' be on the oppo- 

 site side of the Ehizopod 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, important details may be noted. These are similar in 

 both Rhizopods, being rather more conspicuous and more eas- 

 ily seen in Actinosphxrmm eichhornii than in Adinophrys sol, 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 The quickly produced appendages are either slowly withdrawn 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 disappear, or they are smoothed out by ihe 

 gradual dilatation of the swelling vesicle. 



