1872.] 



Modes of Origin of Infusoria §c. 



255 



diminution in the reflectiveness of the separated elements, and their 

 assumption of a more distinctly vesicular character, whilst they simulta- 

 neously acquired a faint brown colour. They were thus converted into 

 unmistakable Fungus-germs, although they showed very little tendency to 

 germinate ; and it was not until after repeated examination that a few of 

 them were found growing out into filaments such as are represented in the 

 figure. Occasionally, in the same pellicle, the embryonal areas broke up 

 into products of a somewhat different character (fig. 5,g, g") . The segments 

 were slightly larger, whilst they gradually assumed a deeper brown colour and 

 a more compound character. These elements also grew at this stage, and 

 underwent processes of division after the fashion of Lichen-gonidia, and in 

 a manner similar to what I had observed on a previous occasion*. These 

 germs also exhibited very little tendency to germinate, though on one or 

 two occasions they were seen to have grown out into short chain-like 

 filaments, such as are represented in fig. 5 g . 



During all the period in which the embryonal areas were breaking up 

 into these corpuscles, which soon assumed the form of brown Fungus-germs, 

 not a single Monad or Amoeba was to be seen in the solution ; and yet 

 it had been standing during the whole time side by side with the other 

 infusion which was prepared at a temperature of 120°-12f>° F. Facts of 

 this kind have been observed on several other occasions with great con- 

 stancy ; so that one may safely state that Fungus-germs or Monads and 

 Amoebae may be procured at will, by simply regulating the amount of heat 

 at which the infusion is prepared. The Monad and the Amoeba represent 

 more highly animalized modes of existence, which are only able to manifest 

 themselves in infusions in which the organic matter has not been too much 

 deteriorated by the influence of heat. Such deterioration seems to manifest 

 itself by altering the developmental potentialities of the primary forms of 

 living matter evolved in the infusion f. 



Experience has shown me that, if an infusion has been heated for a time 

 to 212° F., the pellicle which forms on its surface very frequently never 

 gives rise to an embryonal area. If the infusion has been prepared at a tem- 

 perature of 149°-158° F., the embryonal areas which form will give origin 



* See ' Nature,' 1870, no. 35, p. 173. fig. 3. 



f Seeing that the Monads and the Fungus- germs are produced, not from invisible 

 germs,but from the segmentation of large embryonal areas, evei*y stage of whose formation 

 can be accurately traced, this seems the only possible explanation. If the opponent of Evo- 

 lution contends, in answer to one set of experiments with heated fluids and closed flasks, 

 that Monads are met with because their germs are capable of resisting a temperature of 

 275° F., he cannot now contradict himself by saying that embryonal areas, formed on 

 infusions which have been prepared at a temperature of 158° F., do not yield Monads 

 because such a temperature is destructive to their germs. Neither is it open to him to 

 say that Fungus-germs (derived from embryonal areas) do not appear in infusions pre- 

 pared at 212° F. because such heat is destructive to them, when at the same time he 

 vehemently contends, in answer to other experiments, that similar Fungus-germs are not 

 hindered from developing after exposure to such a temperature, or to others which are 

 much higher. 



