124 British Association. 



" On a new genus of Mollusca Nudibranchiata** By Messrs. Alder 

 and Hancock. 



This new genus is founded on the Tritonia arbor escens of authors 

 and its allies, which are distinguished from the true TritonicB {T. Horn- 

 bergii, &c.) by the form of their tentacula, and the free, arborescent 

 nature of their branchiae. These characters alone induced the authors 

 to consider them generically distinct before they had an opportunity 

 of examining their internal structure, in which such important dif- 

 ferences in the digestive organs were exhibited as to show that this 

 new genus, for which the name of Dendronotns is proposed, should 

 be removed from the family Doridce to that of Eolida, to be placed 

 first in order, as the connecting link between these two families. 



" On the Cilia and Ciliary Currents of the Oyster." By the Rev. 

 J. B. Reade. 



The author stated that in a microscopic investigation of infusoria 

 which had for some years occupied his attention, he had been led 

 particularly to notice the beautiful contrivance by which many spe- 

 cies, when not exerting their powers of locomotion, are supplied with 

 food. When they are examined under the microscope by such an 

 arrangement of transmitted light as makes the infusoria luminous 

 points on a perfectly dark field, it is immediately seen that the action 

 of the cilia attached to their tentacula produces a strong current in 

 the water, and hereby a countless number of minute living organisms 

 is brought within the influence of the cilia, and a sufficient supply is 

 selected for food. Thus with respect to infusoria it is a known fact, 

 that the absence of the prehensile organs possessed by larger crea- 

 tures is compensated by this delicate but efficient ciliary apparatus. 

 It is also a fact equally well known, that the lips of the oyster which 

 surround the orifice of the alimentary canal are in the same manner 

 fringed with cilia ; and that these cilia of the oyster, as of infusoria, 

 equally cause currents in the water. But it has never been suggested 

 and proved by any naturalist, that the proper office of the cilia of 

 oysters is to bring to these acephalous moUusks that food which they 

 have no power to follow or to seize. Such however, without doubt, 

 is the case ; and accordingly an examination of the contents of the 

 stomachs of oysters discovers to us their infusorial food ; and after 

 undergoing the process of digestion in the stomach, the siliceous 

 shields of these infusoria, deprived of their organic and carbonaceous 

 integuments, are ejected as effete matter. In a paper communicated 

 last year to the Microscopical Society of London, on animals of the 

 chalk still found in a living state in the stomachs of oysters, these 

 infusoria were described and enumerated. The apparent identity ex- 

 isting between these recent living infusoria and the fossil makes the 

 inquiry of considerable interest to the geologist ; for the addition of 

 this connecting link to the chain of organized beings extends a con- 

 tinuous line of the same organic structure from the secondary for- 

 mation to the tertiary, and seems to preclude the supposition of 

 Prof. Phillips, that below the tertiary formation are no recent species. 

 Whether or not this conclusion be admitted, it is a fact, ascertained 

 by pursuing this inquiry, that the oysters and other bivalves, which are 



