104 APPENDIX. 



of their collocation, that it would be difficult for an ex- 

 perienced observer to distinguish slides, mounted with 

 the respective organisms, from each other; although 

 one group is from deposits of unfathomable antiquity, 

 and the other from the British Channel*. 



The guano from Ichaboe, when long digested in di- 

 lute hydrochloric acid, leaves a siliceous residuum, which 

 consists of shields of Coscinodisci and other marine 

 Infusoria, of exquisite beauty. 



Entozoa, or internal Parasitical Animals'], note to p. 

 86. — Though the hypothesis enunciated in the text, 

 which is founded on the doctrine of the celebrated Her- 

 yey — "omwe vivum ah ovo^^ — satisfactorily accounts for 

 the presence of Infusoria and other minute organisms 

 under ordinary circumstances, and is sanctioned by 

 direct observation to an almost unlimited extent, yet 

 there are peculiar states and conditions under which 

 animalcular life becomes developed, that are inexpli- 

 cable in this view of the subject ; and are, indeed, in- 

 comprehensible in the present state of our knowledge. 

 Such, for instance, as the occurrence of the various 



* See my " Notes of a Microscopical Examination of Chalk and 

 Flint," in the Annals of Natural History, August, 1845. 



t The Entozoa live in the internal parts of other animals ; and some 

 of the Entozoa are themselves infested with parasites. 



