4:54: EA-EXINGS AT THE MICEOSCOPE. 



tudinal axis, the line of the vesicles alternately ap- 

 proaches and recedes from that of the mouth. They 

 are remarkable for their structure. Far from the sim- 

 plicity in whicli the organ is usually presented to us in 

 the animals of this class, the contractile bladders are 

 here very complex. Each when distended is globular; 



PARAMCECnjM. 



and it is surrounded by a number of others of much 

 smaller dimensions, and of a drop-like form, so set as 

 to radiate round the principal vesicle as a centre, the 

 rounded portion of each in apparent contact Avith the 

 vesicle ; and the slender extremitv running off as an 

 attenuated point till lost to sight in the sarcode. The 

 main vesicles alternately become distended, and sud- 

 denly contract to a point; -while the radiating cells are 

 continually varying in size, though in a less degree. 

 It is customary to describe the secondary vesicles as 

 coming into view at the instant of the contraction of 

 the primary one, and to suppose that the emptying of 

 the one is the filling of the other ; hut I have not been 

 able to observe this mutual relation satisfactorily made 

 out. The smaller as well as the larger vesicles are 

 conspicuous from their colourless transparency ; for 

 the ger.eral sarcode of the body, though pellucid, is 

 only so in the same degree as glass, sliglitly smoked ; 

 besides that its clearness is often impaired by crowds 

 of granules and minute globules. 



