2 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY, 
throughout the whole world of organized living creatures. Such 
reactions must have been developed in the very beginning of the dawn 
of hfe when the first living cells commenced to synthesize organic products 
from the inorganic materials of the:r environment by the use of the store 
of energy from the sunlight. Later on organisms arose which were only 
dependent upon the light at second-hand, since they were able to 
consume the synthesized organic products formed by other organisms 
converting the hght energy directly, and so were only indirectly 
dependent upon the light for their existence. Even for this type of 
organism, utilizing the light energy indirectly, reactions to hght 
remained essential in the search for food and for other physiological 
functions, and also there would be an inheritance of relationships to 
light derived from the earlier ancestry with direct dependence upon light, 
At a later stage structures or organs arose specially adapted for 
hght reactions, and in those living creatures possessing such organs there 
probably came a deterioration of the sensitiveness to light of the 
remaining cells of the body. But in spite of all such decline in direct 
sensitiveness to light, there must have remained some trace of their old 
primeval relationships to light. 
Experimental evidence of this persistence of relationship to light of 
all cells exists of two kinds; there is first the deleterious effects of 
complete withdrawal of light for prolonged periods, and the necessity of 
sunlight for healthy existence; and, secondly, there is the direct evidence 
of the effects of application of strong light to animal cells seen in the 
Finsen effects, and in other forms of radiant energy allied to heht. 
It is, however, in the more lowly organized types of both animal and 
vegetable organisms that the strongest and most direct reactions to hight 
are observable—apart from the particular case of the reaction of chemical 
synthesis in the chlorophyll-containing cells of the green parts of the 
higher plants. ; 
Examples of this reactivity are seen in the effects of sunlight upon 
nearly all types of bacteria; in the sudden outburst of vegetable life in 
the form of diatoms in the spring of each year as the length of the day 
increases and the more vertical light reaches and penetrates the water 
