444 Dr. Griffith on the Sacculi of the Polygastrica, 



mulated without passing through some communicating canal ; 

 this canal is part of the intestinal tube. The minute alimentary 

 particles which arrive in the sacs entire could not be conveyed in 

 that state by solution and imbibition. Moreover we cannot, I 

 think, wonder at our not being able to detect the walls of the 

 tube; first, because, as I have previously mentioned, the elasticity 

 of the substance of the animalcule would keep the walls in con- 

 tact except where actually distended ; and secondly, the minute 

 size of such a canal, and our being obliged to view it through the 

 substance of the animalcule which intervenes between the sacculi 

 and the upper surface of their bodies as lying under the field of 

 the microscope, is well calculated to prevent this. Could we make 

 a delicate transverse section of their bodies, we might then perhaps 

 be able to perceive the tube. M. Dujardhr's objection to the ex- 

 istence of an intestine in Infusoria, " that no fibres remain when 

 the animal is decomposed by diffluence," is undoubtedly futile ; 

 it must indeed require a subtle imagination to expect we can see 

 or even contemplate the size of the fibres of the intestine of the 

 Polygastrica, whose diameter, did they exist, must be almost be- 

 yond the power of calculation, much more of vision. That the 

 masses of colouring matter which have been received into the sac- 

 culi revolve or circulate, as it has been called, is a truth which is 

 very readily proved. Currents are established by the oral cilia ; 

 particles floating or suspended in these currents are drawn into 

 the mouth of the minute creature, these then enter the body one 

 at a time, and apparently accumulate in one of the sacs (t. e. really 

 accumulate in the upper portion of the alimentary tube) ; this then 

 moves down one side of the animalcule ; others are filled in the 

 same manner. The circulation, as it has been called, of these 

 alimentary boluses may then, after having been distinctly followed 

 down one side, be seen returning in an ascending direction. In 

 some cases when these masses have arrived near the oral extre- 

 mity they can be detected approximating the depression by which 

 they entered, until at last their contents are gradually ejected; 

 when the masses are solid, this ejection often takes place par- 

 ticle by particle; when in the liquid or semifluid state, in a 

 fine stream ; the sac can be seen emptying itself of its con- 

 tents; it then disappears. In some of the animalcules this 

 movement of particles may be very readily detected ; it is very 

 tardy in others, and seldom visible at all times. The addition of 

 reagents to the liquid in which they live produces effects some- 

 what similar to vomiting or purging ; the motion of the alimentary 

 boluses is increased, and their ejection is easily viewed ; weak so- 

 lutions of potash or sether produce this effect. Now in all these 

 cases of movement I am convinced that it is not the sacculi or 

 stomachs which move : we must recollect the sacs are made visible 



