FEEDING OF CREPIDULA. 



467 



collecting and transporting the food, the fronto-lateral, which assist in 

 food-collecting, and the ab-frontal or inner cilia, which help in pro- 

 ducing the main current, in collecting food, and in cleaning the 

 filaments. 



Since the ciliation of the gill-filaments in all Lamellibranchs is 

 essentially the same (see Kidewood, 13, p. 163) doubtless in all Lamelli- 

 branchs the main food and respiratory current is caused by the lateral 

 cilia, while the collecting 'and transporting of food-material is done 

 mainly by the frontal cilia, assisted by the latero-frontal cilia when 

 these are present. 



£c. 



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ahfe. 



Fig. 17. — Transverse section of gill-filament of outer left gill-lamella of Mytilus eduHs 

 taken near the free end of the lamella and between the ciliary junctions. ( x 418.) 

 I.e. Lateral cilia which lash in the direction indicated by the arrow alongside, 

 l.f.c. Latero-frontal cilia which lash in the direction indicated by the arrow, 

 f.c. Frontal cilia, 

 ab.f.c. Ab-frontal cilia. 



X. CILIATION OF THE GILL OF NUCULA. 



The ciliation of the gill-plates of Nucula is, I find, essentially the same 

 as that of the gill-filaments of Mytilus (compare Figs. 15 and 18). The 

 lateral cilia are well developed, and, as in the other Lamellibranchs 

 examined, produce the main current through the mantle cavity. The 

 frontal cilia collect and lash food-particles from the tip of the outer 

 towards the tip of the inner leatlet on both gills. The larger frontal 



* This section was obtained from material preserved in Bouin's Picro-forniol (see 19, 

 p. 76) and stained in borax-carmine and jiicro-nigrosin solutions. Picro-nigrosin after 

 picroformol or corrosive-acetic is an excellent stain for cilia. 



