198 Development of Monas Lens. [^jZrnLXrnTim! 



Where the quantity of air and hght is limited, Mucedinae arise. 

 Where air is freely and light sparingly admitted, Monas passing to 

 Paramoecium is found ; but where air and light are freely applied, 

 Monas passing to Gonidium and Euglena may be expected. In 

 liquids where moisture is diminishing, Oscillatoria seem to arise. 



The Soridium of Chlorococcus is white in moist dark holes, as 

 decayed elder trees and moist banks ; green in exposed surfaces, and 

 yellow on stone walls, passing either to green with Apothecia or to 

 yellow Thallus and subsequent Apothecia, forming Parmelia parie- 

 tana; in damp places, as bottoms of palings or doors, Lyngbya 

 results, while in very damp and rather shaded positions, Cladonia 

 pixidata.* 



These, with numerous other modifications, as Collema Lecanora, 

 &c., afford infinite evidence of a tendency to variation, of what, by 

 tracing connections aided by microscopical research, would seem to 

 owe their origin to Monas Lens, or some other elementary germ, 

 whose difference is too minute to come within the reach of our 

 present microscopic vision. 



It may be observed that Dr. Hicks traces the origin of the 

 lichens, &c., no farther back than Chlorococcus ; but with aU defer- 

 ence to so close and accurate an observer, it may be suggested that 

 experiments on Monads and their kindred organisms show that 

 they are entitled to further examination as the probable more 

 remote, though possibly (as Professor Beale suggests) by no means 

 the ultimate source of the Protozoa.f 



Note. — Nov. 30. The lungs of a rabbit, placed in two pints of 

 water in deep glass jar, in dark cupboard ten days ; result, Mucor 

 Mucedo. Liver, heart, and kidneys, in two pints of water in glass jar, 

 exposed to light ten days ; result, Vibrions, Monads, and Paramoecia. 



Professor Tyndall has shown that the rapidity with which air 

 passes through red-hot tubes causes much variation in the amount 

 of organisms and vegetal matter evidenced. This throws light on 

 the dispute beeween Pasteur and Jeffries Wyman. But the vitahty 

 of germs is shown to be very tenacious by Vaucher's observations on 

 frozen water. 



Attention must also be paid to the pabulum afforded to these 

 organisms ; for we find that as ozone is present or absent so does car- 

 bonic anhydride vary in evolution. Certain substances prevent, 

 others admit of, while others, again, promote their growth. 



Besides the experiments on various liquids, there is evidence, 

 from the varied states of growth which make their appearance on 

 inland stone walls, marine stones, trees, stagnant pools, running 

 water, shallow streams, deep seas (see Bathybius), drainage from 



* See Hicks on Chlorococcus, Cladonia, Lyngbya, Nostor, &c. 

 t Protoplasm, pp. 72, 3. 



