Account of Professor Ehrenherg's 



tudinal division, or of propagation by gemmae, which he had 

 observed in the same species of animals in other circumstances. 

 The animals remained a few days without change ; their bodies 

 then appeared somewhat contracted in the middle, which ap- 

 pearance was an indication of commencing division ; when 

 this had once begun, they increased very rapidly, so that, in one 

 case, a three-fold division was observed to have taken place in 

 the course of twenty-four hours, a single animal having multi- 

 plied to eight. 



2. Individuals, after undergoing division several times, were 

 observed alive for ten days, to which time, at least, the duration 

 of their life must therefore extend. 



Dr Ehrenberg lastly infers, as a general result of his inquiry, 

 that the origin of infusory animalcules can be, in all cases, satis- 

 factorily accounted for without the necessity of having recourse 

 to the doctrine of spontaneous generation, which he regards as 

 a mere hypothesis, not required to account for known facts, and 

 unsupported by any trustworthy observations. 



Without undertaking to advocate the theory of spontaneous 

 generation, we may be permitted to remark, in opposition to his 

 conclusion, first, that the supporters of the doctrine by no 

 means deny that animals which owe their origin to spontaneous 

 generation may and do afterwards continue their species by 

 propagation, whether by ova or otherwise ; that the fact of the 

 increase of existing infusoria by propagation, which is the chief 

 argument furnished by Dr Ehrenberg's observations, was pre» 

 viously known, and therefore forms no new argument against 

 the doctrine. 



2c%, It might be objected, that the animals submitted to 

 observation in the cases related, belong to the larger and more 

 perfect species of infusoria, and are therefore less likely to be 

 produced by spontaneous generation. 



3JZz/, That although Dr Ehrenberg, in refuting the notion 

 of the extreme simplicity of these animals, has overthrown 

 one great argument in favour of their spontaneous origin, 

 yet he has oflPered no explanation of their production in infu- 

 sions which have been subjected to a heat sufficient to destroy 

 any parent animals, or even ova, supposed to be present. In 

 these cases, as is well known, the adversaries of the theory 



