of the Flints of the Uppet^ Chalk. 301 



fore necessarily be false ; and none who see the structure of the 

 inclosed object perfectly preserved, while not a trace of the struc- 

 ture of the alleged incloser can be found, can for a moment 

 doubt which generalization must be abandoned. 



But we come now to another and most important point, to 

 which I request the special attention of the reader ; and I cannot 

 imagine that any one who applies the rules of inductive philosophy 

 to scientific investigation can contemplate the facts I have now 

 to name without at once feeling that the sponge theory is utterly 

 untenable. It is necessarily a postulate of the sponge theory, 

 and is distinctly stated by Mr. Bowerbank (page 255, &c.), 

 that, in every case where a Ventriculite is encased in flint, it is 

 in consequence of the parasitic growth over the Ventriculite of a 

 foreign sponge. I have in my cabinet at least 500 specimens 

 (probably very many more) of Ventriculites. I have shown Mr. 

 Bowerbank the greater part of these, and he was not able to 

 point to more than one single specimen (and that very doubt- 

 fully*) in which a parasite had not overgrown the original body, 

 and so formed the flint. Now it is not enough to tell us of in- 

 stances of parasitic sponges, nor yet that certain species are 

 always parasitic. It must be demonstrated that there existed 

 species, having a special and peculiar affinity for silex, which 

 were invariably parasitic ; and that there was invariably present 

 silex in precisely sufficient quantity to saturate them. It must 

 further be proved that this species of parasites had the wonderful 

 property of always growing in pairs, one growing inside and the 

 other outside of the invested object, and yet having no possible 

 connexion with each other, though, with very rare exceptions, 

 growing to precisely the same level. It must further be proved 

 that the Ventriculites themselves, unless thus invested, never could 

 become silicified ; that, when invested by the parasite, they were 

 always silicified. It must yet further be proved that the parasite, 

 though retaining its form, invariably decomposed utterly before 

 that process commenced in the invested Ventriculite. Further, 

 it has been seen that the law of non-organic union of different 

 species is never observed by these particular species of assumed 

 parasites. This is a pretty long draft on our credulity. Now I 

 request the reader to note that, having before me hundreds of 

 Ventriculites invested with flint, and hundreds not invested with 

 flint, there is not one solitary instance in which any para- 

 sitic sponge is found in the chalk and unsilicified to surround a 

 Ventriculite ; nor is there one single instance in which, the Ven- 

 triculite being invested by flint, a trace of the alleged parasite is 



* This case really forms no exception. Mr. Bowerbank declares even the 

 specimens named by me at bottom of p. 8 and top of p. 9 to be invested with 

 threads of the parasitic sponge. 



