ON CILIARY MECHANISMS. 301 



current-producing cilia analogous to those of Gastropods, Lamelli- 

 branchs, Ascidians, Amphioxus, and Brachiopods. 



The function of these spines is being investigated further, and figures 

 will be given to show their resemblance to gill-filaments. MacBride, how- 

 ever, is doubtless correct in stating {Camb. Nat. Hist., Vol. I, p. 550) that : 

 *' Between the two posterior petals (in Echinocardium cordatum) there is a 

 hoop-shaped band of very small black spines. These spines are ciliated, and 

 draw a current of fresh sea- water over the respiratory tube-feet. Beneath 

 the periproct there is a similar band called the ' sub^anal fasciole ' ; this 

 probably produces a current of water which sweeps away the material 

 ejected from the anus." 



THE CILIARY MECHANISMS ON THE GILLS OF CRYPTO- 

 CEPHALOUS POLYCHvETES AND ON THE LOPHOPHORE 

 OF PHORONIS. 



An examination has also been made of the cephalic gills of various 

 Cryptocephalous Polycheetes. It has been found that these gills are 

 used for the purpose of feeding, and that the ciliary mechanisms con- 

 cerned in the feeding process in — for example — Spirorbis, Pomatoceros, 

 Hydroides, Branchiomma, Sabella, and Filograna are identical with 

 those on the gills of Lamellibranchs, some Gastropods, Amphioxus and 

 Brachiopods, that is to say, there are well-differentiated current-pro- 

 ducing lateral cilia and food-collecting and food-transporting frontal 

 cilia on the pinnules of the tentacles. Food is very rapidly collected in 

 these Polychsetes and transported along the pinnules to the axes of the 

 tentacles and thence to the mouth. Further particulars and figures with 

 regard to these animals will, however, be given later. 



The lophophoral cirri of Phoronis have also been investigated, but up 

 to the present it has only been possible to examine the living animal 

 cursorily. Nevertheless this short examination revealed the facts that 

 in this animal also the cirri — or gill-iilaments — are differentiated into 

 lateral and frontal rows, and that a good current of water is drawn 

 towards the mouth within the space enclosed by the lophophoral cirri. 

 The functions of the lateral and frontal cilia in Phoronis, however, do 

 not appear to be identical with those of the similar cilia in Brachiopods 

 and the other groups mentioned above, but a more complete examination 

 of the living animal will be made later with a view to investigating fully 

 the ciliary mechanisms concerned in process of feeding in this animal. 



