CHALK MAKERS, OR FORAMINIFERA. 31 



It has been contended that there exists an in- 

 ternal circulation in the body, because when the 

 animal pushes out a lobe, or prolongation, a rush 

 of granules will be seen flowing in the direction of 

 the new foot or lobe. Dr. Wallich contends that 

 the flow is merely mechanical, and this view is 

 generally accepted. " In the large jSseudopodia of 

 Amceba" he says, "we see at once that the ap- 

 pearance of an advancing and a retrograde current 

 is due to the fact that the lower surface of the 

 organism is fixed, as it were, to the plane on 

 which it rests, whereas its upper or free surface 

 only is being projected into pseudopodial exten- 

 sions. In short, the effect is identical in character 

 with that which would present itself, if, after filling 

 a transparent and highly-elastic bladder, with some 

 viscid and transparent fluid in which granular particles 

 of slightly greater specific gravity than the fluid itself 

 were suspended, we were to roll it slowly along a 

 flat surface. In such a case, the upper stratum of 

 granules would in reality be moving forwards in the 

 direction in which the bladder was being rolled ; whereas 

 the inferior stratum, although at rest, would appear 

 to be retrograding ; for the same reason that when 

 a railway train is slowly and steadily put in motion, 

 the platform appears to be moving from the ob- 

 server seated in one of the carriages. Now, as 

 regards the cyclosis, this result could not take 



