812 Microscopical Society of London. 



induced him to examine the contents of the stomach, under the ex- 

 pectation of finding some minute forms of Infusoria, which, in the 

 absence of locomotive power, compensated by the beautiful contriv- 

 ance just alluded to, might reasonably be expected to form the food 

 of the creature. His expectations were fulfilled. In the stomach of 

 every oyster examined by him, he found myriads of living Monads ; 

 the Vibrio was also in great abundance and activity, and swarms of 

 a conglomerated and ciliated living organism, to which he proposed 

 to give the name of Volvox ostreare. But the most remarkable cir- 

 cumstance was the presence of other Infusoria, having siliceous loricae, 

 belonging to the family of the Baccillariae, and similar to those which, 

 in the fossil state, constitute the chief bulk of the chalk. They were 

 the following : — 



Actynocyclus fasciola Dictyocha fibula Xanthidium furcatum 

 Coscinodiscus minor speculum hirsutum 



putina Gallionella sulcata Zygoceros rhombus 



radiatus Navicula entomon surirella, and two new 



Dictyocha aculeata Tripodiscus Argus species of this genus. 



The whole of these, together with some other well known species of 

 Baccillaria and Polythalamia were found alive in the stomachs of 

 oysters. Having thus established the identity of the present Infusoria 

 which form the food of oysters with the fossils of the chalk, he next 

 proceeded to examine the contents of the fossil oysters of the Kim- 

 meridge clay; and in these, as well as in the surrounding clay, he also 

 found abundance of similar fossils. 



The inferences drawn from these observations were : — 1. That the ci- 

 liary movements of oysters, and, from analogy, those of other bivalves, 

 are the means by which these creatures are supplied with food, con- 

 sisting of minute Infusoria and Polythalamia ; which food, from the 

 absence of sand, and other extraneous bodies, they evidently have the 

 power of selecting : and, 2. That many of these Infusoria being simi- 

 lar to those found in a fossil state in the chalk and other secondary 

 formations, supply that link in the great geological chain of organized 

 beings, formerly supposed to be wanting, between the cretaceous and 

 antecedent series and the series of subsequent formations. 



Mr. Reade also made some observations *on the probable effects of 

 heat upon organic remains ; and concluded by quoting the opinion of 

 Ehrenberg, that " since of the four as yet well established geological 

 periods of the earth's formation, the quaternary, tertiary and secon- 

 dary formations contain recent organisms, it is as three to one more 



