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JOHN W. SCOTT. 



draw in toward the membrane blood cells from a considerable 

 distance; these cells therefore hit the cilia with some force, but 

 the major stroke of the cilia is strong enough to bounce them off 

 again, usually driving them away five to ten times their own 

 diameter, and frequently beyond the limits of further attraction. 

 However they may bounce two, three, or four times, that is, 



FIG. 2. To show a portion of the fimbriated membrane found at the inner end 

 of a post-diaphragmatic nephridium of Amphitrite. Not so much magnified as 

 Fig. i. The membrane is undulating at a, and folding to form a groove at b; at c 

 is the deep main groove leading into the nephridial sac; at d, are pillar-like projec- 

 tions overhanging the main groove. For further explanation see text. 



until they reach the region of the groove shown at b, Fig. 2 ; then 

 the cilia on the sides carry them up, out, and away. Only in 

 very rare instances do blood cells ever reach the main groove; 

 sometimes they follow the eddy near a mature egg, but they are 



