GREGARINIDA, RHIZOPODA, BPONGIDA, AND INFIsouiA. 13 



l'V. 3. 



D 



m 



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C 



m ■ ' i 



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-?,'■'■''-■. 

 / ■ 



Fig. 3. — A, Hypothetical section ot a Spongilla ; a, supeincial layer; 6, inhalent aper- 

 tures; c, ciliated chambers; d, an exhalent aperture; c, deeper substance of the 

 sponge. The arrows indicate the direction of the currents. B, A small sponge with 

 a single exhalent aperture, seen from above (after Lieberkiihn); a, inhalent apertures ; 

 c, ciliated chambers ; d, exhalent aperture. C, a ciliated chamber. D, a free- 

 swimming ciliated embryo. 



