Natural History of the Vortlcellse. 389 



according to this, the chyme when already elaborated into a 

 homogeneous granular substance (or, to anticipate no opinions, 

 the fundamental substance of the circulating paste) is not at 

 all sarcode or protoplasm in the sense applied to the term by 

 authors. For the movement of rotation, as careful examina- 

 tion shows, is not that of a tenacious, contractile substance ; 

 it does not manifest itself after the fashion of the amoeboid, 

 slowly creeping protoplasmic streams with which we are else- 

 where aquainted, but it progresses everywhere easily and 

 briskly, sometimes even with a sliglitly tremulous current, 

 through the inner space. But how is this to be brought into 

 agreement with the phenomena of motion which we are always 

 accustomed to witness in the tenacious contractile protoplasm, 

 and which must be regarded as characteristic of the latter. 

 Is not the vibrating movement rather a proof that it is per- 

 formed by a readily flowing, non-contractile substance, i. e. 

 precisely not by protoplasm ? Moreover, we must here again 

 call attention to the phenomenon already insisted on in the 

 examination of the cortical layer surrounding the body-cavity, 

 according to which the current is briskest at the outer walls. • 



Stein requires also, as evidence of a body-cavity, that this, 

 when its contents are evacuated, must also appear as an 

 empty cavity. If we could effect a transverse section through 

 the body of a Vorticellan (which, however, does not seem 

 possible, considering the minuteness and delicacy of the 

 object), we should, I have no doubt, be able to bring the body- 

 cavity under direct observation ; but even the examination of 

 the uninjured living animal satisfies this requirement. Thus, 

 if we isolate for a time in clear water, upon a glass slide or in 

 a watch-glass, a newly captured Vorticellan with its bell dis- 

 tended with food, we may see how the food-balls are ejected 

 one after the other. The body gradually becomes paler and 

 more elongated ; the walls acquire folds ; and after the lapse of 

 a certain time the well-fed convex Vorticellan becomes a slim 

 collapsed animalcule, the integuments of which sink here and 

 there into the evacuated stomachal cavity in deep folds and 

 sinuosities. 



But, instead of food, water is now taken up through the 

 nutritive tube ; and according as the access of this is abundant 

 or scanty, the body-cavity becomes filled out or not so com- 

 pletely collapsed as above indicated. At the same time, how- 

 ever, the remarkable phenomenon which is very characteristic 

 in the question now before us makes its appearance — namely, 

 that the movement of the contents is much brisker than be- 

 fore, and may generally be recognized in a distinct vibrating 

 current of the form-constituents still mixed with the water. 



