S8 MANUAL OF ZOOLOGY. 



6. The nature of the vibrios and bacteria must be looked 

 upon as quite uncertain. To say the least of it, they are quite 

 as likely to be plants as animals ; and the most probable hypo- 

 thesis would place the former near the filamentous Confervse, 

 or would regard them as the mycelium of various species of 

 Moulds (PeniciUium). 



c. What has been said above with regard to the origin of 

 the bacteria and vibrios applies equally to the origin of the 

 Monads, which appear in the infusion subsequently to the 

 death of the vibrios. 



d. These Monads, as shown by recent researches, are pro- 

 bably to be looked upon as the embryonic,- or larval, forms of 

 the higher Infusoria which succeed them. 



e. Many of the Infusoria which finally appear are of a 

 comparatively high grade of organisation, being certainly the 

 highest of the Protozoa, and being placed by some competent 

 observers in the neighbourhood of the Tremiatode Worms 

 (Annuloida). It is therefore very unlikely that these should 

 be generated spontaneously ; since, if this ever occurs, it is 

 reasonable to suppose that the creatures thus produced will 

 be of the lowest possible organisation (such as the Gregarinidcfe 

 or the Monera, for example), and will be far below the Infusoria 

 in point of structure. 



f. The reproductive process in many of these same Infusoria 

 is perfectly well kiiown, and it consists either in a true sexual 

 process, for which proper organs are provided (as in Pararhoe^ 

 cium), or in a process of gemmation or fission. It is there- 

 fore improbable that they shoilld be generated in the manner 

 maintained by the heterogenists, since this mode of reproduc- 

 tion would appear to be superfluous. 



g. In the absence of any direct proof to the contrary, it is 

 safer to adopt an explanation of the observed phenomena 

 which does not have recourse to laws with which we are as 

 yet unacquainted. Thus, it is not at variance with any known 

 law to suppose that the primary molecules are the result ot 

 the development of germs which find in the inorganic infusion 

 a suitable nidus ; that these primary molecules and the vibrios 

 which they produce are referable to the Protophyta, and 

 should probably be placed near the filamentous 'Confervse ; 

 that by the death of these vegetable organisms the fluid is 

 prepared for the reception and development of the germs of 

 the Protozoa, for which the former serve as pabulum; and 

 that many of the forms which are observed are the larval 

 stages of the higher Infusoria.* 



* Recent researches, especially those of Dr Bastian, have established 



