44 J. H. ORTON, 



SUMMARY OF THE ACCOUNT OF THE CILIAEY 

 CUEEENTS IN SOLENOMYA. 



The main current througli the mantle cavity is effected by means of the 

 lashings of the lateral cilia on the gill-leaflets. This current is drawn in 

 at the antero-dorsal region of the shell and expelled in the posterior 

 region. The food-particles brought to the gill in this current are arrested 

 on the gill by the latero-frontal and frontal cilia, the former passing on 

 particles to the latter. The frontal cilia transport the food-particles 

 along with mucus, which is doubtless secreted by the epithelium of the 

 gill, on to the ventral edges of the lower leaflets, whence a special group • 

 of cilia transport the collected particles and mucus towards the mouth 

 to be eaten.* Ciliated knobs occur on the ab-frontal edges of the leaflets 

 which serve to interlock with similar knobs on the fellow-leaflets on the 

 other side of the body. Long interlocking cilia also occur at the dorsal 

 ends of the upper leaflets and the ventro-lateral edges of the lower ones. 

 These cilia serve to effect a junction of the gills with the mantle during 

 feeding, and so divide the mantle cavity into an inhalent and an exhalent 

 chamber. 



On the whole, therefore, it is seen that the gill of Solenomya, like that 

 of Nucula, is essentially similar to that of the higher Lamellibranchs. 

 Indeed the presence of numerous ciliated knobs must rank this gill as a 

 more highly specialized one than, for instance, that of Anomia aculeata,. 

 which has only interlocking arrangements at the tips. Apart from the 

 narrowness of the filaments in A. aculeata, there is almost an exact 

 resemblance between the gills of this species and those of Nucula and 

 Solenomya togata. Thus the gross structure and the function of the gills - 

 in the Protobranchia and the Eilibranchia have been shown to be essen- 

 tially similar, and there caai be Very little doubt from the published 

 accounts of the gills of other Pfotbbranchia that these may be regarded 

 as essentially similar to those of Solenomya and Nucula. 



THE FUNCTION OF THE GILL IN LAMELLIBEANCHS. 



The gill in all groups of Lamellibranchs has now been shown to be a 

 feeding organ. Generally, however, this organ is regarded as being 

 chiefly a respiratory and only secondarily a feeding organ. In the light 



* Since this account was sent to the printer, a paper by E. S. Morse on Solenomya 

 in the current number of the Biological Bulletin, Woods Hole, has come to hand. 

 This paper gives an account of observations on living Solenomya velum and S. borealis. 

 Morse has observed the palps being used for transferring food from the gill to the mouth,, 

 which fact, added to those given above, completes our knowledge of the mode of feeding 

 in Solenomya. 



