of the Flints of the Upper Chalk. 9 



penetrated the internal structure, none being found encasing 

 either the external or internal surface*. This would clearly be 

 inexplicable on the sponge theory, but presents itself as a fre- 

 quent phsenomenon in several of the classes of objects above 

 enumerated, and is consistent with the observed fact, already no- 

 ticed, of the affinity of the silex for soft animal matter. When, 

 moreover, flint is found enveloping the outside of a Ventri- 

 culite, it is almost invariably found enveloping it, to exactly the 

 same extent and no more, on the inside, and this without the 

 edges of the Ventriculite being at any point overlapped. It is 

 obvious that no sponge can have possibly grown in this manner. 

 Again, the delicate roots of these bodies are very frequently in- 

 deed, more frequently than any other part, found preserved in 

 flint, a fact in most diametrical opposition to the very funda- 

 mental and necessary postulates of the sponge theory, as the 

 sponge would clearly lie upon, not penetrate into, the mud. Yet 

 these ventriculite roots are thus commonly found, while it is ad- 

 mitted that no place of root is to be found belonging to the so- 

 called sponge masses themselves. I have a specimen in which, 

 in one block of chalk, there are five Ventriculites. The stem and 

 root of each one, and no other part, is enveloped in flint. 



It may here be noticed as an interesting and important fact, 

 that it will be found, on careful examination, that not only is the 

 internal structure of the Ventriculite preserved, but, in fine spe- 

 cimens opened with care, the integument of the animal, which 

 presents quite a difi'erent structure, is also preserved, covering over 

 the internal structure ; and thus at the same time disproving the 

 alleged sponge character of the Ventriculites t, and showing that, 

 at the time when the silex aggregated round and penetrated the 

 Ventriculite, this integument was unbroken. So in Choanites, 

 which have quite a difi^erent exterior, that exterior will be fre- 

 quently seen perfect, clear and distinct, while exterior to it is a 

 layer of flint. 



It will be obvious, that if the sponge theory is to be taken as 

 any explanation at all, it must assume, in addition to the inad- 

 missible postulates already noticed, the inconceivable phaeno- 

 menon that every one of these living bodies was penetrated by 

 the sponge, since the very object of the theory is to show that all 

 the spaces now occupied by flint were once sponge, that is, that 

 silex has precisely replaced sponge and nothing else. If it does 

 not go this length it is of no value whatever as a theory, since 



* It is worthy of particular remark, too, that all these bodies are very 

 frequently found only partially enveloped in flint, the remainder of the 

 body being found in the adjoining chalk. This affords clear demonstration 

 against the sponge theory, but space will not allow of my entering on this 

 very interesting class of facts. 



f See Prof. Ansted's paper above cited. 



