high degree of fit. Equations for varying numbers of time observations from 

 the start of experiment were calculated. A comparison of correlation 

 values, calculated for different functions, shows that they are largest for 

 power and parabolic functions, suggesting that these equations describe the 

 regularity more accurately. 



This conclusion was correct for varying concentrations of TMTCh. The 

 power function IgN = a + b IgT, where N is number of dead Daphnia , in per- 

 centage, and T is the time in days, in logarithmic coordinates becomes a 

 straight line (Figure 1), and it is possible to construct the curve based 

 upon two points. Examples of the transformation of regularity of Daphnia 

 mortality with time in logarithmic coordinates for organic tin and other 

 compounds are given in Figure 2. It should be noted that the experimental 

 and calculated values are not close enough. This fact is reflected by low 

 values of correlation coefficients. It is possible that fluctuations de- 

 pend on factors that are difficult to take into account in calculations, 

 e.g., varying development of adaptive processes in organisms, and their al- 

 tered reactions to environmental influences when exposed to different con- 

 centrations of compounds. 



An attempt to analyze the dynamics of mortality in toxic solutions was 

 made in order to understand the relationship of observed regularities to 

 time. It is obvious for both groups of organisms, and for individuals, that 

 they are influenced by the solution of toxic compounds, and that the toxic 

 reaction increases through time, either as a function of continuous accumu- 

 lations of the toxic materials, or as a result of the volume of alterations 

 in the organism. The outcome for individual Daphnia will be the increasing 

 of probability of death, and for a test group, there will be an increasing 

 ration and rate of mortality. Thus, the slope of the curve increases dra- 

 matically in acute lethal experiments with organic tin compounds. In 

 chronic studies, the curve progresses in a step-wise form. This reflects a 

 sudden reduction in the rate of mortality with continuous exposure to toxic 

 influences. 



The explanation for this phenomenon lies in a combination or sum of two 

 processes, (1) mortality under the influence of toxic substances, and (2) 

 acceleration and enhancement of adaptive process^^s within the organism that 

 inhibit mortality (Figure 3). The increase in toxicity proceeds more or 

 less regularly with time, forming the basis for the adaptive processes that 

 occur after the development of harmful effects in response to the toxins. 

 It is not yet clear what activates these adaptive processes, the level of 

 compound, the results of the deleterious effects in tissues, or the rate of 

 increase of accumulation. It is possible to determine the rate of decrease 

 or absence of mortality in toxic concentrations. Both of these two compo- 

 nents, harmful effects and adaptation, can be described by adequate equa- 

 tions that can be used for further elementary analysis of the dynamics of 

 the curve of mortality. However, the unique reactivity of living systems 

 under the influence of toxic substances complicates the regularities that 

 could describe the results of toxic effects. However, after calculating the 

 coefficients a and b for the equation of power function, it is possible, 

 with high degree of probability, to calculate the mortality of any percent- 

 age of Daphnia for a given period of time. 



142 



