1878.] the Influence of Light upon Protoplasm. 201 



The rays which were found to pass through each glass respectively 

 are given below. 



Blue. — Violet, blue, some green, broad band in yellow-green, very 

 narrow band in ultra-red. 



Yellow. — The whole spectrum, except violet and about half the 

 I blue. 



Bed. — Red, orange-red. All other rays entirely absorbed. 



The mean of a number of observations as to temperature showed 

 that, at the point at which we worked, viz., 70° — 80° F., the ther- 

 mometer in the red box stood about 2° F. higher than in the lead- 

 incased tubes ; between the blue, yellow, and ordinary glass boxes 

 there was but little difference, the blue being about half a degree 

 warmer than the last named. 



We showed in our former communication that by increasing the 

 density of our cultivation-liquid the development of Bacteria could be 

 proportionately delayed. In this way we have been able to accentuate 

 the differences in the behaviour of the solutions under varying con- 

 ditions of light. Without detailing all the experiments, we may say 

 that the first tubes to become turbid were the lead-incased ; the next, 

 usually in from 24 — 48 hours subsequently, the red, followed shortly 

 by the yellow ;* white and blue surviving. 



The organisms which first appeared in the lead -incased and red 

 were always Bacteria ; in the yellow, usually Torula, or mycelium, with 

 more or less Bacteria, — rarely Bacteria alone ; if organisms appeared 

 in the blue or ordinary glass they were torulaceous. 



Although the blue and yellow glasses were not monochromatic, we 

 think that these results give important indications. That the action 

 is chiefly dependent on the blue and violet rays is shown by the great 

 difference, as compared with those in the blue box, in the behaviour of 

 the tubes in the yellow, in which, as we have already stated, the only 

 rays of the spectrum not admitted were the violet and part of the 

 blue. 



Moreover, the fact that when the cultivation-fluid is of sufficient 

 concentration the red (although the warmer) survives the lead-incased 

 shows, we think, that the red and orange-red rays are not altogether 

 inactive. 



It is probable therefore that, if the phenomena were represented by 

 a curve, the maximum elevation would be found in or near the violet, 

 a rapid descent occurring in the blue or green, after which the line of 

 the curve is maintained more or less as far as the visible red. 



The experiments next to be detailed bear upon the part played by 

 the cultivation- fluid in the phenomena under consideration. We had 



* The only instance out of a large number of observations, in which yellow broke 

 down before red, happens to be the experiment described in our former communica- 

 tion. 



