470 Miss M. Greenwood. On the Constitution and [Dec. 14, 



matter and subsequent shrinking, both varying in character and 

 extent, are common accompaniments of the fundamental chemical 

 reaction of clotting. 



In Carchesium, then, it may be that we meet with a modification of 

 the process, that there is an iiitravacuolar discharge of matter which 

 clots, shrinking rapidly, and not with the slow change of casein or 

 fibrin, and that it, entangling any solid particles which are present, 

 brings about the spasm of aggregation. The substance is, indeed, not 

 demonstrable usually by staining or other form of micro-chemistry, 

 but delicate indicators of the presence of acid introduced into a 

 digestive vacuole indicate that the vacuolar fluid begins to have an 

 acid reaction about the time when aggregation is perfected. It is 

 conceivable, then, that an access of acid fluid at this point may help the 

 effective retraction of the clot, or even its first formation. 



When by the process of aggregation spherical ingesta have been 

 welded together in the substance of Carcliesium from digestible or 

 indigestible particles, they journey through the " endoplasm " in a 

 fairly constant fashion, but for a variable time. Occasionally they 

 are stored for hours after loss of the fluid of those vacuoles in which 

 aggregation occurred ; at times the digestion of nutritious matter 

 follows the preliminary clustering with no marked pause. All 

 nutritive ingesta present are not of necessity digested synchronously ; 

 indeed, there is sometimes apparent caprice in solution, but certain 

 features of the process are invariable whenever its onset occurs. 



Thus, as in Amoeba, solution is effected in a fluid medium. The 

 stored up food masses of Carchesium, when they have lost their 

 fluid surroundings, have reached the extreme point of density and 

 shrinkage ; solution implies swelling, transparency, and re-formation of 

 a vacuole if it has not persisted. Digestion may take place at any 

 point throughout a relatively large part of the central substance of 

 Carchesium, buu complete solution is extremely rare, and innutritions 

 remains travel with varying rapidity towards the anal ridge from 

 which they are discharged. Thus they pass into the pharynx, to b& 

 swept to the exterior eventually by ciliary currents. It may be said 

 that, other things being equal, the intracellular sojourn of ingesta 

 tends to vary directly with their digestibility ; thus clusters of aggre- 

 gated particles in which such bodies as carmine or Indian ink pre- 

 ponderate or stand alone have a relatively short time of enclosure ; 

 the fluid of the vacuoles in which they are formed often disappears 

 quickly, and there is but rarely (in the case of unmixed innutritious 

 matter) that re-formation of fluid which is so nearly concerned in the 

 solution of true food stuffs. 



I have spoken hitherto with some vagueness of the duration of 



