294 J. H. ORTON. 



of a filament of Argiope is figured by Shipley (4), who depicts uniform 

 cilia on three of the four sides of the filament. Examination of the liv- 

 ing filaments* and sections of specially preserved material, however, would 

 doubtless show that a differentiation of cilia occurs here as on the filaments 

 of Crania, Rhynchonella, Terebratula, and other forms. Blochmann, 

 however, has given beautiful figures of transverse sections of the gill- 

 filaments of Crania, in which the differentiation of the lateral and frontal 

 cilia is very well shown in a section of a filament of the dorsal series, but 

 less well in that of a ventral filament. This writer also gives rougher 

 figures of Discina and Lingula, without, however, figuring the cilia, but he 

 remarks that the filaments of these two forms are essentially similar in 

 their characters to those of Crania. Hence there can be no doubt that 

 the gill-filaments of all Brachiopods have cilia disposed and differentiated 

 in the same way as in Crania. 



SUMMARY OF CURRENT-PRODUCING MECHANISMS AND THE 

 MODE OF FEEDING IN BRACHIOPODS. 



The main current through the mantle cavity in Brachiopods is pro- 

 duced chiefly by the lateral cilia on the gill-filaments and partially by 

 cilia on the mantle and on the body of the lophophore. The disposition 

 of the lophophore and the filaments on the lophophore is such that two 

 ingoing currents of water are established at the sides of the mantle 

 cavity. On each side the current passes between the filaments of the 

 first turn of the lophophore and outwards through the filaments of 

 the second and succeeding turns of the lophophoral spiral into the 

 median dorsal region of the mantle cavity. At this point the currents 

 from each side meet and pass out of the mantle cavity at the middle of 

 the anterior region of the shell. 



The food-particles brought into the mantle cavity in the main stream 

 are caught by the frontal cilia on the gill-filaments, and by those on the 

 outer frontal portion of the lophophore, and transported by these cilia 

 into the buccal groove. In the buccal groove the food-particles are lashed 

 rapidly along to the mouth by the strong cilia on the buccal lip and fused 

 bases of the filaments. It seems probable that the food-stream in Brachio- 

 pods is effectively sieved by the gill-filaments, since besides collecting 

 food-particles the ventral ones lash directly on to the food-collecting 

 face of the lower filaments which alternate with them : moreover, part 

 of the food-stream is repeatedly sieved in most forms by the filaments 

 on the superposed whorls of the lophophore, 



* Subsequent examination of living Argiojie from Naples has shown this statement 

 to be correct. 



