The Conditions of Infusorial Life. 91 



blue and violet coming next, and then white light, red being 

 inimical. M. Morren had stated that the action of light was 

 indispensable to the production of vegetable organisms, and 

 that if a series of vessels filled with water were exposed to a 

 more or less intense illumination, those with least light exhibited 

 fewest protophytes and of the most simple construction; but 

 M. Pouchet on repeating his experiments came to an opposite 

 conclusion. In one instance he placed a piece of crumb of 

 bread in a large glass, covered it with three black shades, 

 and placed the whole in a situation of complete darkness. In a 

 week the surface of the bread was covered with blue mould, 

 Penicillmm glcmcum, between the filaments of which were 

 swarming an abundance of Monas lens, and several vibrions. In 

 another instance M. Pouchet placed, in a dark corner of his labora- 

 tory, an infusion of hay, covered with a bell-glass painted black, 

 over which was put a strong sheet of gray paper, and over this 

 again another black shade with a roll of linen round its base. 

 The whole of this apparatus was further protected against the 

 intrusion of light by double curtains, black, and tawny ffauvej. 

 In three days, the temperature being warm, the liquid was 

 covered with a thick pellicle, while monads, vibrions, and kolpods 

 were abundant. 



The passage of a current of electricity through the infusion 

 materially hastens, according to M. Pouchet, the production of 

 infusoria, his experiments being performed with one element 

 of Bunsen's battery. Atmospheric electricity afforded still more 

 striking results : the more it abounded, the faster the infusoria 

 appeared, especially if the tension, instead of being suddenly 

 produced by a storm, lasted for several days. Under such cir- 

 cumstances he obtained kolpods as highly developed in three 

 days, as woidd have been obtained, with the same temperature 

 and less electrical excitation, in double that time. 



Contact with mercury, and mercurial vapours, had no in- 

 jurious effect on infusoria; and, contrary to what had been 

 affirmed by M. Morren, air which had traversed sulphuric acid 

 neither killed them nor hindered their production. A wooden 

 cover, almost touching the infusion, exerted a favourable influ- 

 ence ; and the shape of the vessel was important, so far as it 

 promoted, or hindered, the action of light and air on the fer- 

 mentable matter. 



It has been explained that M. Pouchet endeavours to prove his 

 theory of heterogenesis by an exhaustive process of experimental 

 reasoning. He seeks to show that the supposed germs do not 

 exist in the air he employs, nor in the water, nor in the putrescible 

 solid ; but still the infusoria appear — produced, as he believes, by 

 the same vital force that presides over the generation of the higher 

 animals ; and which, he tells us, " engenders in the ovaries of 



