FEEDING OF CREPIDULA. 



453 



to obtain a fair idea of the spacial relation of the inhalent chamber. 

 Fig. 7 is a transverse sectional diagram of the inhalent chamber, and 

 Fig. 8 a longitudinal sectional diagram, A in both figures indicating the 

 position of the forwardly directed stream in the inhalent chamber. 



GILL FILAMENT 



IN- GOING 

 CURRENT 



Fig. 7. — Diagram of the special relations of the mautle eavit}' of Crepidula in transverse 

 section, taken just anterior to the propodium. 

 A indicates the position of the forwardly directed stream. 



JNHALENT ^ 

 CttAMBE/i- 



/N-GO/NG 

 CUff/?£//r 



G/LLf /LAMENTS 



£X//AL£/Vr 

 ^^''C//AMB£/? 



oar-Go///G 



Fig. 8. — Diagi-am of the general spacial relations of the mantle cavity of Crepidula in 

 median longitudinal section. The inhalent and exhalent apertures are repre- 

 sented, although not actually occurring in the section. 

 A indicates the position of the forwardly directed stream. 



It will be seen that the area of the inhalent aperture is relatively 

 small, and that there is a sudden widening out at this point of the path 

 of the inhalent stream. Consequently, when a current is passing 

 through the mantle cavity the velocity of the stream must fall just 

 inside the inhalent chamber, and as a result the larger particles tend 

 to lag behind and sink in the stream. As they sink they come 

 within the influence of the forward stream caused by the cilia on the 

 food-pouch, mantle and left epipodium, and becoming eventually caught 

 in this stream (see the small arrow A in Figs. 7 and 8) are carried 

 forwards into the food-pouch. From the disposition of the cilia causing 

 the forward stream, it is possible for the coarser food-particles always 

 to be carried forward, no matter whether the animal be placed upside 



